In reply to Dax H:
A somewhat convoluted string of events ended up with me taking a £40k thermal camera home from uni for a couple of evenings.
Spent a lot of time imaging the cats' footprints as they walked across the floor (visible for a good 10-20 seconds) and my own heat reflection from walls and windows. Great fun.
Also, my flat leaks LOADS of heat, but I knew that anyway.