It is, indeed! We are software developers (jfbaro and rarduin) and would like to build a open source device to help rescuing people after disasters. We are still developing the idea, but I think it's feasible. Please, check the projects page: **broken link removed**
The problem here is that the victim could have wood, metal, concrete over he/she and that would difficult quite a bit the measuring. But if, after a signal being detect, we could say to the Emergency workers the device had detected someone in such a region (or less, if there is loads of obstables - wood, metal...) I think it would be still helpful for them. What are your thoughts about it?
P.S.: As you probably imagine, we are not trying to make any money of it, the main goals are: 1) Helping people; 2) Learn a bit about the subject.
Cheers