I've got a Micromark system from Homebase above my garage door, It is hooked up to a portable 14" TV & VCR so if anyone comes within 6ft of the door, it records for 30 seconds, this can be altered but I find it enough, It is black & white so can also be seen at night, The camera always shows a picture even when not recording, The problem you may have will be if the car is on the road, there will be a lot of movement near it causing lots of video tape to scan, Micromark have a website,
Hope this helps,
Pete