these are accually becoming quite common. Animes tend to make special editions or bundles that include a mousepad with a bust. Hentai based ones r the best :P
I think my dignity and pride would rather have my wrists slashed off before I used one of these. I mean, hey, boobies. Cool. But this is taking it a little far. Once you have these (and a oppai ball, with its life-like texture ;_; ) it's time to seriously reflect on your life and priorities.
I bought one of those mousepads with the "theraputic wrist rests" and not only did it not work, but it made my carpal tunnel worse. So I highly doubt these ones are any better.
Actually, I really wish that there was a place locally that made custom ones, or that I could at least find a good template and proper do-it-yourself measurements. I'd love to have one just as a conversation starter, but I haven't liked any of the ones I've seen for sale.