Advanced Ringer Rocker emulates the Android 2.1 volume rocker button behaviour which allows you to enter vibrate or silent mode using the volume buttons.
With this app enabled, pressing Volume Down results in:
[Normal → Vibrate → Silent]
Pressing Volume Up results in:
[Silent → Vibrate → Normal]
This functionality was removed by Google in Android 2.2, as it confused some users.
This app causes the following side-effects
• If you manually change from normal to vibrate mode (i.e. without using volume keys), you will need to press the volume down button twice to enter silent mode.
• Every time you turn off silent mode (e.g. via settings or the lockscreen), it will always then enter vibrate mode instead of normal mode. i.e. You need to swipe the lockscreen silent slider twice to leave silent mode