The good people at GOOD tip us to SoBi, an emerging model of bike-sharing set for test launch in New York City this fall. The "social bicycle system" takes a minimal approach to the idea of public bike share. Instead of custom bikes and an elaborate network of docking stations, SoBi uses a single, mulitfunctional gadget that fastens to the back of any bike and operates as a lock, GPS unit and bike computer.
A mobile app (what else?) tells users the location of any available bikes nearby. After the ride, you just lock it up anywhere and another user can grab it and go. It's a neat idea, one that substantially reduces the costs associated with conventional bike share.
SoBi is currently in the running for a Pepsi Refresh grant. If you're into it, give them your vote.