Cute commerical idea, free to good home

[nancylebov]

If you use a bat detector, you can hear rats laugh. Why not sell bat detectors to people who would enjoy hearing their rats? Maybe another transducer could help people talk to their rats.

This looks like something that would take some capital--or at least a fast googling didn't turn up any bat detectors for sale, though there were directions on how to make your own.

Video link from kip_w.