In January, OnStar announced an API would allow third party developers to integrate their applications with OnStar's platform. Last week, General Motors announced its first partner for API integration: RelayRides. RelayRides is "[t]he world's largest peer to peer carsharing marketplace." The partnership with GM allows OnStar users to leave their keys in their cars when renting a car to a fellow RelayRider. The renter can then unlock the car with a smartphone app or by responding to a text message.