Thanks to Mystic's Muses I just came across an organization in Africa that uses rats to not only find land mines but detect Tuberculosis.
Talk about a low-tech solutions to important problems.
No need to call PETA, either. The critters are not sent to their deaths. They're actually too light to set the pressure plates off, and the website's FAQ explains that a trained rat is far too valuable to sacrifice, too.
APOPO trains sniffer rats to detect explosives and diagnose disease. This unusual idea has been developed into a competitive technology by a group of Belgian and Tanzanian researchers and animal trainers.
Speaking of rats, the DVD for the animated film "Ratatouille" has a very funny and informative bonus film about rats' place in history.