Heater for the car.

[DEL 707]

I like to chill out in the car doing lunch break, but it's starting to get a bit nippy.

I've been looking something that I can plug into the cigarette lighter to warm up the car.
There seem to be quite a few different products around, but are they worth while?
Also, how quickly is something like this going to drain my battery?

 

[DEL 707]

Gone low tech.
Bought a blanket.