build a black box spy camera from a digital camera and a pir sensor, works just the same way as a truvelo speed camera,but this is portable but you don't have to go past it at great speed, keeps on taking pictures until the xd card gets full.
Step 1: Fully Automatic Spy Camera
built from an old Fuji digital camera, pir switch it is powered by 2 18650 batteries, i chose a fuji with a slide cover on off switch, connected the pir to a relay board the output then triggers the camera on and also drives a motor when rotates slowly it operates a switch with takes a picture. when you trigger the pir it turns the camera on extends the lens and starts taking pictures of you, if you stay in range it will continue to take pictures, if not it will close the lens and turn off, it also has a flash, one 18650 battery powers the camera, then both 18650 power the pir which has a low standby current. just leave it to take pictures then come back later and remove the memory card and download the images it has taken.