For example, General Motors is teaming up with RelayRides so that owners of GM vehicles will be able to use the automaker's OnStar system to provide quick access to their car without the owner and the renter ever having to meet.

As it is now, renters and owners have to meet to hand off the keys or a separate device has to be installed on the car to allow renters access with a magnetic card.

OnStar currently has 6 million active subscribers and another 9 million cars have OnStar hardware installed, ready to be activated. That makes for a huge pool of available cars for potential customers, said Clark.