I know Home Adivsor uses it, and a bunch of other major corporations are using it also. Basically when you close a deal, instead of emailing over a contract to be printed, signed and sent back, you just activate the voice contract signing. It plays a series of messages to the person who then agrees to them by speaking or hitting certain numbers on the dial pad.
I've tried searching for this, but so far I've only come across one provider and I'd like to see more.
this is the one I've found so far.