BlackBerry app that runs in background and intercepts all times a key is pressed?

I would like to create an application for my BlackBerry that intercepts every time I press a special key, like the "End call" button or "lock screen" button. I want it always running, and without a GUI.

Targeting OS 7.0 is ok, if necessary.

Could you please point me to the right direction? What classes should I look for?

BlackBerry apps that are in the background can't listen for key presses. They can still register listeners that will be called during certain system events (screen locking, incoming call, for example). As far as just flat out being sent key strokes, it's not something they have any sort of API for.