Get their license plate number. Call the cops. Just about all you can legally do.

Last week I looked up plans on the internet to jam cell phones.
We sat in a movie theator next to a couple of young girls
that didn't talk on the phone but they sat there and text
messaged the whole time. Guess they thought it was ok since
they weren't talking but the blue light of the screen was
too much to take. Should have gotten an usher. But sure
would be nice to just be able to jam the signal.
I found several plans thru google. Mite investigate them.
They are illegal. Use at your own risk.

Pooh Bear

sounds like this would be good for MYTHBUSTERS!!!