SoundBlink Hacks allows to control sounds on a simple level. Basically it allows you to mute or redirect any sound from any application at a given time.
You can define for a given period of time that all sounds should be muted and that the LED should blink instead. Or that certain applications should usethe vibrating facilities of your device. SoundBlinkHack allows you to define this on a per-application basis.
Palm OS 4.x