How to Set Up a Door Open Chime/Siren
There are several reasons why someone why someone would want an audible alert in the house when a door is opened, rather than just a text or push notification.
For example, if you have a child who wanders, you might want the adults to wake up if a particular door is opened at night.
Or you might want the equivalent of a doorbell if a front gate is opened.
There are many different contact sensors available for use with SmartThings which can detect the door being opened. That part is easy. The question is how do you set up a device to make an audible alert when the sensor send the "door opened" message to the hub?
As of the February 2017, there are a few chime Devices available that work with SmartThings, including one that allows you to upload your own sound files. However, some options may require the classic app. There are several different ways to make this work depending on what you were trying to accomplish.
All of these options will require that you also have a contact sensor on the door that you are monitoring, or some other device to notify SmartThings of activity. You will need one sensor per door. These generally cost around $20 each although they can sometimes be found on sale as low as $15.
Once you have set up the basic alert (door opens, sound plays) if desired, conditionals such as time of day, mode, etc. can be added through the usual SmartThings logic.
Alternatively, maybe you don't want a chime when the door opens, but you want a chime in a different part of the house when the doorbell button is pushed on the outside of the house. In that case, you can either use the Aeon doorbell which comes with its own button or you can get the Nexia doorbell sensor which is wired into your existing nonnetworked chime and will inform your SmartThings hub when that chime sound. Or you can use any of the fancy video doorbells like Ring which have a SmartThings integration. Then you use that "doorbell pressed" event as the trigger to have other chimes sound elsewhere in the house. And again, you can use SmartThings to add additional conditionals like mode or time of day.
Getting a Spoken or Sound Effects Alert from Amazon Echo When a Sensor is Triggered ( works with the new app)
As of 27 August 2018, Amazon now offers a new feature that allows you to have any smartthings – connected contact or motion sensor trigger a spoken alert on your Amazon echo devices. Or if you have sound effects files in your music library yet, you can play one of those. That could be a chime, a buzzer, a siren, etc.
You will do this with an Amazon echo routine (not a SmartThings routine). It's very simple to set up. Official Alexa Instructions. You can have the same Amazon echo routine turn on lights.
You could also have the Amazon echo routine turn on a virtual switch which then triggered other smartthings events.
For many people who already have Amazon echo devices, this may be all you need, as long as you're OK with a chime/announcement which depends on the Internet working. If you need something that will work when the Internet is out, look at the power outage alert or alarm clock alert options below.
As long as you are using an actual physical sensor, you can do this with the new app and the official options.
SmartApps that support Chimes, Sirens and Notifications
Here are some community built SmartApps which can monitor devices and notify you through various means:
1. Chimes and Notifications for Doorbells and Sensors This app supports Chimes, SMS, Push Notifications and Text To Speech (TTS) Notifications and can monitor contact sensors, locks, presence sensors, tampers, switches and buttons. It requires a paid license to RBoy apps.
Using the Built-in Chimes In the ADT Model Hub
If you have the SmartThings ADT model hub and the dual logo ADT/SmartThings Door Sensors, you can set up one of about a dozen different Voice or chime notifications for each of those sensors using the “security options” for the individual sensor in the app. This works with either the classic app or the new app. Some of the choices include a doorbell type sound, a triple beep, voice announcement, etc. The sound will play only on the hub itself. It can only be set up to work with the dual logo sensors, not any of your other sensors. And this option is only available for this model hub.
Devices to Make a Chime Sound Once SmartThings Recognizes the Trigger Event
1A. The Aeon Doorbell 5 ($69) (Requires the Classic App)
One very straightforward solution is to get the $69 Aeon doorbell. This has two parts: a Z wave speaker and a wireless button remote for the speaker. You can use the button as a panic button or a doorbell button.
For the purposes of this how to, though, we are only interested in the speaker unit. This device can play up to 99 different custom sound files, so you can make anything you like from a Windsor bell to a spoken notification. It also comes with some built-in sounds including a chime. You can trigger the speaker with a SmartThings command, which means you can play different tracks for different SmartThings events, including a door sensor recognizing that the door is open.
So the solution is fully integrated with SmartThings, gives you many different sound options, and you can use any trigger event that SmartThings can recognize.
There are two negatives. First, the device can be quite fussy to get paired initially, with some people reporting that they have to try 15 or 20 times. (This pairing difficulty is the main reason for the low Amazon ratings.) Secondly, the device will require custom code. There are two different community-created Device type handlers, both approved by the doorbell manufacturer, which work very well and offer slightly different features. And people in the community will be glad to help you get things set up. But it's not quite as simple as just using the official "add a new device" feature.
Still, once you get this device set up the way you want it, it will solve most of the use cases that people have. You can also use different sounds for different doors.
Note that you need to get the "doorbell" model, not the "siren" model so you can upload your own sounds.
UK Note: this device was originally manufactured on both the US and the UK frequencies, but since it was first released, the UK version has become very difficult to find. So you may not be able to use this option in the UK.
Community discussion thread with the device type handler code: ]
Amazon listing 
In 2019, Aeotec released a new version of this, the Aeotec Doorbell 6 ZW162A. Available for both the US and the UK at a similar price to the original, but with a nicer looking button. This one comes with 30 different sounds, but you can no longer upload your own file. It will require the following custom device type handler.
2. Dome Chime ($35) US Only) ( requires the classic app)
This is a Z wave plus device, introduced in the second half of 2016, which has 10 built-in tones and an optional signal light. This solution is fully integrated with SmartThings, is inexpensive, but limits you to the 10 built-in sounds. (A similar device is also sold under the zooz brand.)
3. UEI / Xfinity Keypad Model XHK1 with Tone ($10-$20) (US Only) ( requires the classic app)
UEI makes a Zigbee security keypad which has a built in tone. There is only one tone sound, it also has a motion sensor and temperature sensor build into it. It runs on 4 AA batteries (Lithium, Alkaline or rechargeable NiMH/NiCd). Same device is also sold for the Xfinity home system.
eBay listing 
4. Lowes Iris Keypad Model v2 (3405-L) and v3 (iL021) with Tone and Siren/Alarm ($49) (US Only) ( requires the classic app)
Lowes makes a zigbee security keypad which has a built in tone. There is only one tone sound. Earlier v1 models were not compatible with SmartThings, so check the model number. The Iris v2 has a built in 60dB Siren while the Iris v3 model has a built in 85dB Siren which can be used an Alarm in SmartThings. This requires the use of the Enhanced ZigBee Lock Keypad device handler
There are several different custom device type handlers available for it, each with slightly different features. These are available on the quick browse list in the device Type handler section on the security list.
Lowe's listing 
5. Ring Doorbell with Optional Chime Unit (US AND UK) ( May work with the new app, needs verification)
The ring video doorbell has an official integration with SmartThings and also has an optional plug in Chime unit so it will ring like a regular doorbell as well as giving you phone notifications. The video doorbell itself runs around $180, and the optional plug-in chime is usually around another $25. Both are available from Amazon in both the US and the UK.
Official support article: https://support.smartthings.com/hc/en-us/articles/214288206-Ring-Doorbell
6. Power Failure Alert plus SmartThings power outlet (total $35-$55) (Both US and U.K. Choices, but with different brands) (Works with the new app)
If you want a more annoying sound, perhaps to discourage a family member from opening the door, or you want a solution with A very easy set up, you can purchase a "power failure alarm," plug it into any networked power source that works with SmartThings, and use the official "smart lighting" feature to turn the power source 'off' when the contact sensor reports "door open." That way when the door is opened, SmartThings will turn off the power to the alarm, the alarm detects the power loss and sounds its beeper.
The beepers are typically loud and annoying. People use them without a home automation system for freezers or even medical equipment that lose power. They cost anywhere from $15-$35 at Amazon or any home-improvement store. You also need to purchase a networked power supply device that SmartThings can control, typically a pocket socket for about $20.
Most people won't want these for a doorbell, but they can be useful as a deterrent for family wanderers.
You also will have several options for how to turn the beeper off again. Just turning on the networked power source will do it. Some people will have things set up so just the door closing again will turn off the beeper, but that's not usually what you want for a wanderer alert. Instead, you may want to just use the official phone app and toggle the switch, or put a button on the wall. But again, to SmartThings this is just an outlet that's being turned on and off, so you will have a lot of choices.
At $15, the reliance controls plug in power failure alert is a good choice for a beeper device when you want a "door open" alarm which is not as overwhelming as a typical security siren, but is still annoying enough to be a deterrent. . There are many similar brands as well. You also need to purchase a SmartThings – controllable power outlet, typically around $20. So this specific setup should cost a little less than the Aeon Doorbell, but only has one sound option.
Most of these devices can be set up to operate even when the Internet is out as long as your smartplug and sensor run locally with SmartThings.
7. Alarm Clock Alert (Price is the cost of the clock, plus $20 for the outlet) (Works with the new app)
Before the Aeon doorbell and the zooz chime were available, some people would use the same set up as the power outage beeper, but would instead plug in an alarm clock of the kind where once the alarm sounds, it continues to sound until you press the button, and if you unplug it in the middle of sounding and then plug it back in again it continues to sound once the power comes back on. So for this set up you just have SmartThings turn on the power to start the alarm clock sounding and turn off again to stop the sound.
This generally gives you a choice of sounds which are less annoying than the power failure beepers. Some are even suitable as doorbells. The trick is to find one that will go right back to sounding when power is restored. Some models will, some won't, so you may just have to try a few. (If the clock has a battery backup feature, do you not use it – – just take out the battery. You want the clock to be off when the power is off and on when the power is on.)
For this method you still have to buy all three devices: contact sensor for the door, alarm clock for the sound, and networked power source so that there is something for SmartThings to control. Set up is easy, and you can just use the official smart lighting feature. If you already have a alarm clock you can repurpose, then the cost will be lower than the Aeon Doorbell. But this solution will be limited to only one sound option.
And again, this option can run locally as long as the sensor and the smartplug run locally.
8. Various Text to Speech(TTS)/Custom Sound Speakers (cost varies, but is typically $150 and up) (Some options will work with the new app, it depends on the device)
Some speakers have the ability to play custom sounds or spoken announcements, such as Sonos, Bose SoundTouch, or Samsung's Multi-Room Speakers. If you have such a speaker, you can use a smartapp called "Speaker Companion" to trigger sounds from SmartThings events. To install it, open the mobile app, tap on the marketplace icon (asterisk icon in the lower right), choose "smart apps" at the top of the screen, scroll down until you find "music and sounds" and open that. This will then list the officially published smart apps in this category. Look through the list until you find "Speaker Companion" and select it.
All of the devices in this category cost more than the simple alert devices or the Aeon doorbell discussed above so in most cases you would only choose this method if you already had the speaker device for other reasons.
Using the Echo Speaks integration for Alexa, you can now have Alexa speak notifications. This requires the use of compatible SmartApps which support Text to Speech (TTS) notifications.
9. Android as an Audible Alert (requires an android phone/tablet) (Requires classic app)
The LANNouncer app for android (formerly called Landroid) requires an android device. Set up is fairly complicated, but this gives you a lot of different function options. Essentially lets you use an android device in the same way that the TTS speakers work. Community discussion thread with links to the software 
Smoke Detectors, including the Nest Protect, Cannot be Used for Custom Alerts
Residential Smoke detectors sold in the US have to meet a number of specific safety requirements. One of these is that the smoke detector announcement system cannot be used for custom alerts. The concern is that you might miss a fire alert because the speaker was busy telling you the laundry had just finished. So these devices cannot usually be Repurposed as door open alerts.
There are some home security systems which are classified as multipurpose alerts rather than smoke detectors, that do have the ability to Play custom spoken alerts for intruder detection, which would include a door being opened. For these, you need to check the details of each individual system to see what is available.
For more information
For help setting up a specific notification, ask in the community forum