^ i just tried it and it worked (not the tennis ball trick, the keyless car entry)
thats on my mom and my dead grandparents
it worked on a beamer, though. i dont know if the quality of the car matters.
one thing tho...when i did it with my cell phone, it didnt open. BUT, the lights came on inside the car. when i did it with the owners of the cars cell phone, it opened...both the trunk and the doors
i dont know if its like some shit where they have the owners cell phone number and it only opens with that cellphone...regardless the phone that worked next to the car was a nokia and mine was a cingular
so thats proof it does work