Effective Car Alarms

I was with a friend in a cafe when a noisy car alarm interrupted our
conversation.

"What good are car alarms when no one pays any attention to them?" I
wondered aloud.

"Some are quite effective," my friend corrected me. "Last summer, my
teenager spent a lot of time over at the neighbor's house. Whenever I
wanted him home, I'd go out to the driveway and jostle his car."