Joel at Boing Boing Gadgets has this splendid microphone ring from Etsy ($105, but sold out, obviously). You could hack the module from a $5 K-Micro condenser mic into a ring, maybe with the phantom powered electronics in a wristwatch...
Posted by Tom Whitwell.
Awesome! This reminds me of the Seiko drum machine watch... is it posible to fit a whole studio on to one arm? maybe arm studios are the next big thing.
Wowza. I'm a nerdcore rapper, but I do a lot of yo-yoing and circuit bending in my shows, a ring watch could be so handy.
[insert ring modulator joke *here*]
As for the pre-amp idea, the Seiko Drum Machine watch is huge. I haven't taken mine apart yet, but it's huge. It'd make a great housing for the amp. Here's mine; http://www.flickr.com/photos/docpopular/1572156813/