Sleep Timer can pause/stop or silence music after a set amount of time and can also turn your screen off.

It works just like a Sleep Timer on TV
Sleep Timer softly lowers the volume and then turns your music off (not all players are yet supportet). If you have watched a stream Sleep Timer can also turn your screen off. This functions prevent your battery from draining.
Simple design and easy to use
Select how long you want the music or stream to play, press Start and Sleep Timer will appear in the notificationbar. You can extend the length or cancel the timer directly from the notification message. (If you have more then one notification, swipe the Sleep Timer notification down to see the buttons.)
Free version
The free version contains ads.
Unlocked version via in-app purchase
Ad-free.
More settings.
How to uninstall (IMPORTANT):
Sleep Timer uses the device administration function, it need to be deactivated before uninstall.
Just use the menubutton "Uninstall" to remove Sleep Timer or go to Settings > Location & Security > Select device administrators -> uncheck Sleep Timer -> uninstall.
Permissions explained:
• Google Play billing service: Unlocked version.
• Internet / network access: Required for Google Play access and bug reports.
• Wi-Fi connections / Bluetooth: Allows Sleep Timer to turn off Wi-Fi/Bluetooth once your music has been stopped.

// Option A //

To download Sleep Timer (Audio & Video) mod from HappyMod.com.
You need enable the option "Unknown Sources".
1. Click on the above link to download Sleep Timer (Audio & Video) mod APK.
2. Save the file in your device Downloads folder.
3. Now tap on Install and wait for the installation to finish.
4. Once it is done, open the game and start playing it right away.

// Option B //

To download Sleep Timer (Audio & Video) from HappyMod APP, you can follow this:
1. Open your browser and download the HappyMod APK file from HappyMod.com - the only official website of HappyMod.
2. Open Android Settings and go into Privacy or Security.
3. Tap the option to Allow Unknown Sources and enable it.
4. Go to your Android downloads and tap the APK file.
5. Follow the directions on the screen to install it.
6. Search Sleep Timer (Audio & Video) in HappyMod App.