Checking whether the screen is locked

[gooz]

Hi,

I'm writing a presence agent application for Android (that checks if you are 'available' or 'away'). For this I would like to check any activity on the phone.
The easiest way to do this would be to check whether the screen is locked. Is there any way to do this?
Alternatively, is there a way to check if the user is 'using' the screen or touching any keys without having to be in the activity of this app (so I can check this from within my service when the user is using other apps).

Thanks in advance!