Keyfob Phone

 I know that in this day and age almost everyone has a cell phone.
I was thinking that most people know where their cell is, but sometimes have a hard time remembering where they put their keys, or fob. So why not have the car recognize your phone. It would work the same as the keyless fob. Walk up to your car with your phone and the car would unlock, start without digging around trying to find your fob or keys! In a woman's purse, or a mans pocket.   Just a thought.