Compact cheap "surveilance" camera

[bitsyboffin@xxxxxxxxx]

A club I am a member of has a problem, members keep leaving the club's
buildings unlocked, unalarmed and even with the doors open on occasion.
 All the members are of course entitled to use the facilities when they
please, they pay for it after all, but the trouble arises because the
last person leaves for the day and either forgets to lock up, or thinks
somebody else is still around.  It's only through pure luck we havn't
been fleeced already.

So what I'm considering is a compact and reasonably cheap solution to
have a time lapse series of digital images taken, ideally, a looped
recording so it can just overwrite old images as it fills up.  That way
when somebody discovers the doors open I can grab the device and have a
look to find who was last there and give them an ear bashing.

Something like the "L'espion S" (
http://www.thinkgeek.com/electronics/cameras/7886/ ) but with a much
larger capacity so it can take and store an image every, say, 120
seconds for a week, and even better if it had "night vision".  Doesn't
need to be colour (8 bit greyscale is fine, only need to identify the
people passing through, not judge thier fashion sense) or high
resolution (probably could get away with 320x240, but 640x480 would be
better).  Battery powered would be best, but I guess it could be
plugged in if necessary, but we don't want to have it connected to a
computer that then has to run 24/7, it would only be connected to the
PC when we need to review the images.

Anybody seen such an item?