IR cameras for outdoor installations using processing

I’m searching for any advice on IR cams (or hackable webcam) that could allow me to track people in a distance of about 20 meters. The most of the hackable webcams I know turns out to have this problem with long distance focus (and even more if you remove the IR blocker). So, anyone could give me any clue on that? In the case of a surveillance camera is needed, I would like to make sure that I’ll could use it with processing. Thanks a lot for any info you could give. Cheers!