i just found that i can get a wireless camera system with audio for 54$ and a cam w/o audio for 45$ maybe less if i can get many of them at one time.
it is a full kit that includes a 20mmx20mm cam
9v battery plug and wall jack for the cam (if you dont want to use the battery)
receiver for the camera with power adapter (can also be ran with a 9v)
and rca cables to plug the receiver into a tv or vcr
the cams have a 100foot range thru walls and 1000ft range in open air
if you are interested drop me an email
i want to grab some for my overland and minix
