That seems to be a Renishaw-type touchprobe, which is basically a needle floated on a set of springs that makes an electrical contact when deflected. This was the first sort of 3D scanning device, originally used on CNC machines for locating a workpiece. Roland Corp of Japan devised an improvement on that technique with a piezo-electric probe that's more sensitive and faster-acting. I've made lots of scans with those devices; they're useful for other things besides keys, but are restricted to flattish sorts of objects. It's a very slow process, though, especially if you want good detail on large parts.

Andrew Werby
www.computersculpture.com