Mark U , Dec 04, 2006; 05:33 a.m.
It depends what you mean by inexpensive and heat sensitive as opposed to IR. True heat sensitive imaging relies on longer IR wavelengths, and few cameras really work well in that territory. You can have a camera converted for IR work:
You can convert a Sigma SD10 yourself:
or you can look for a good IR performer among these cameras:
(look under sensitivity).
Exploring the far IR spectrum comes at rather greater cost: