All they'd have to do is put functions in GPS equipped phones much the same as full blown GPS receivers.

Those phones don't find Mecca becuas it emits a signal, it finds it because it is always in the same place, and uses your GPS location to compute which direction Mecca is, and I think which direction your phone is pointing. My thoght is to use the same software as the Mecca finding phones do, but replace the coordinates of Mecca to those of where you parked your car.

RDF, which is what you are thinking of, is next to impossible wthout either the nack to find RF signals, or complex antenna arrays and equipment.

I think this is a great idea, you just need the cell phone to learn your car's coordinates everytime you lock your door, maybe through bluetooth technology (widely available now a days).... Then, your mobile phone with GPS, could know where you parked the car!!!!!

This could be done using existing hardware. No need to buy a new gadget if you have a newer phone. With the right software instaled your cell phone company can triangulate your position. Download the software to your phone and your away. When you park your car you would locate your cars position in the phone menu. When you lose your car go to the right menu page and it will tell you.

This is not a GPS thing, because probably GPS will show you the mall in the map .. and if the car is underground maybe you will not get anything ... you need something more local, more fine-tunned. You need that your car sends a signal and your phone to catch it. But car cant be sending the signal all the time. Then maybe you equip your car with some sort of celular device that has its own number. So you call your car and it starts to make noises and lightings.