I got a wireless camera off of eBay for, I think, around $28 US shipped. It works fairly well. When powered by a 9V battery it will last well over half an hour, probably more like 45 minutes, though the range does drop off when the battery gets run down. The receiver gets quite warm but it works and that’s all I ever asked for! It has a mic, which is pretty much useless but the video quality is actually amazingly good for the first ~10m LOS. Vibration causes the image to go fuzzy, but gets back to normal if the bot is stopped. It has decent range, I’ve had it go through two solid brick walls (eight inches thick, apiece) and a wall made of drywall and the image is still good enough to safely navigate a bot.
I don’t remember which eBay store I bought it from exactly, but it’s very similar (dare I say exactly the same?) to these two [1] [2]. Remember to specify if you want the PAL or NTSC format camera if you do end up buying one.
