I am exploring this possibility as well. I am in Canada, so that opens some doors and closes others. We should talk as I have found some things out but don't have anything running yet. I know some Canadian Companies that have gliders that would be easily adapted and some good IR cameras. But is always a matter of money. Have you found anything out yet? I was planning on adapting mine to do wildlife counts.
Any suggestion on a particular IR camera ?
I liked the looks of the Tau line from a company FLIR i don't know if there is any stipulations on buyers though.
The link below should be a good start based on your parameters above.
One possible solution but far too expensive from my perspective.
Getting a FAA COA to fly the missions is a bigger hurdle than buying a system.
You should talk with Chris Miser of CLMax Engineering (google his website). He has a system for just your intended use under development, which I consult on a bit and which is quite far along. More importantly he is working with law enforcement agencies to get COA's for flying his system on SAR missions, and it appears that those agencies are having some success in getting the COAs.
I see Chris has a new website for the commercial uav which is falcon-uav.com
i came across RQ-1 style kits on the fleabay for $70 (minus motors servos and electronics) it is feasable to use a weedwacker or similar motor and get a good range and decent payload. most of the cost would be in the FLIR unit. coupled with a contour 1080 i could see a fixed camera with a 130 degree wide angle lens so it could scan a path close to 500m wide at 200 feet or so with good resilution. you would have to develop a program to reconise human sized 'blips' on the FLIR video and triangulat the position relative to the UAV and maybe a IR laser beam firing strait down from the UAV for the third reference point....
the Palm IR pro might be a good choice for the IR camera, very sensative and can be switched between black/white hot and color. B/W might be a beter choice when programing for auto recognition of hot spots. www.nationalinfrared.com/palm_ir_pro.php
err... broken link www.nationalinfrared.com under the products section for hand held devices. it should be easy enough to hard wire the ribon cable going to the display into a RF transmiter. that way the image processing for persons recognition can be done on site or mobile with a laptop.