The idea is simple: You force your kid to keep an iPhone in the car, with the Safe Driver app running. (The app records when and where it's initiated or disabled.) When Junior's home, you review the app's data to determine whether he went for a night of gentle cruising, or a drag race down Main Street.

While the app is free, an in-app purchase for "Safe Driver Pro" unlocks more features: You can even set up custom speed limits and the like--when the car approaches a pre-set limit, the iPhone sounds a warning. And if your not-so-little girl puts the pedal to the metal, Safe Driver Pro can e-mail or text you instantly. The Pro version also can e-mail you a Google map tracing the entire route your kid took, along with a summary of how fast and dangerous he drove.

If you don't mind being Big Brother in addition to Big Poppa, the app may be worth a look. Safe Driver requires iPhone OS 3.0 or later, and works with the iPhone, iPod touch, and iPad.