I think the ones on the market are very overpriced for what they are. Has anyone tried using a Reptile heating cable? You can get a cheap controller for it too ($15 or so) It's mains supply, but you could easily connect it to a 12v if need be.
I'm also looking at making my own straps using
http://www.carbonheater.us/
I rekon it would be fairly easy to hook it all up.
Anyone done anything else similar?
Cheers!