I wrote a little App that locks the Device using WMs built-in password lock.
I didn't like the behaviour of this lock so I decided to set this to 24 hours and lock manually.
You need Windows Mobile 6+ since the aygshell.dll is only available there.
Features:
Lock (and I mean really lock, not starting the lock settings like some other apps do)
Suspend after Lock depending on certain circumstances
Registry (can be set in Settings app)
Commandline Parameters ("suspend" / "nosuspend")