Using V4L as the base for a security system?

["Andrew A. Chen" <achen-v4l-list@xxxxxxxxxxxxxx>]

Hello-
I'm interested in using my V4L compatible capture board in a security 
system that records video only if it detects activity.  For example, I 
would like the system to normally sample only 2fps normally, and if it 
detects activity, start recording at 30fps.  Does an open source system 
like this already exist?  If not, is anyone aware of any libraries that do 
motion detection?  Thanks!

-a