Just a note.
This is a "feature" of the stock camera ui, but the fact that it's missing from this clone is a plus for me.
The stock UI pauses the mediaplayer when it's started and resumes it when it's closed.
Stringing the binaries shows that they both talk to the policy daemon through libplayback.

I'm not sure if you want to implement this, but I like the idea of being able to record videos with the N900 while playing music.