Share your car, says GM, and we'll help you do it (with Onstar)

General Motors says its On-Star customers can now use their GM cars to make some extra money - by renting out their vehicles.

Car-sharing allows someone to rent their personal vehicle to people who don't own one. Typically the borrower just needs a car for a few hours, for errands, grocery store visits or the like.

Now, GM car owners who subscribe to Onstar can rent out their cars through a car-sharing company called RelayRides.

Among other things, Onstar can track a car remotely, and allow access to the car without a key - so the owner doesn't have to meet with the renters to give them the key.

RelayRides and other car-sharing companies provide extra insurance to cover accidents that could happen while the car is being rented, although some insurance companies still frown on the whole concept of car-sharing.