Is there a scheduler or timer app that will allow me to perform a task after certain time. More specifically, I would like to stop the music player and make the phone in sleep mode. Is there any such app?
This app seems to match your criteria
Description: "Set a sleep timer for your currently playing music, so that your music will turn off after you go to bed!
This app is the only one that will stop ALL music playing from your Windows Phone, including iHeartRadio, Slacker, Zune, or any other third party music app. The others can't do that!
- Set a custom timer (hours, minutes, seconds)
- Runs under lockscreen"