RealSilent

Battery-friendly background service that will automatically mute the media volume on your phone when you change the ringer to silent.

Features:
- Ability to mute on silent mode, as well as vibrate.
- Ability to restore media volume to what it was before going to silent/vibrate.

This app will NOT change the alarm volume. It only makes sense, and if you want the alarm volume to be silent when the phone is silent, please do so on your preferred alarm application, most let you change this setting.