Once upon a time, parents had to be pretty crafty to track their teenagers' driving habits. Sure, they could look for obvious signs of recklessness like dents and scratches, but hard braking? Aggressive driving? Almost impossible to spot without tailing them from a distance. (Which, of course, our parents did. ALL THE TIME.)

Today, moms and dads have it easier. Thanks to many high-tech developments, parents can now track and/or control their kids' driving behavior from the comfort of home. Apps and services like T-Mobile's DriveSmart encourage teens to be smarter about texting and driving. Ford's ingenious MyKey technology lets parents limit a driver's speed and the volume of the stereo. Monitors like the Progressive Snapshot work like the black boxes on airplanes, keeping track of major events. And, of course, real black box devices may be required on all cars in the U.S. in another two years.

The extreme end of this monitoring trend is the onboard video recorder. DriveCam -- arguably the most popular of such devices -- stores footage in a cache that's regularly cleared, but when it senses "erratic vehicle movements, such as extreme braking, acceleration, cornering or a collision, the device provides a video clip of what occurred the 10 seconds before and after the event." The camera then wirelessly sends that clip to DriveCam servers so that it can be shared with parents, helping them coach their teens on safe driving behavior.

The American Family insurance company offers the DriveCam as part of its Teen Safe Driver Program; it pays for the cam and the cost of installation, offering an insurance discount in exchange. According to the American Family FAQ, the company doesn't receive video reports from the devices, and recorded incidents won't result in premium increases. That's comforting to parents and seems a lot friendlier than Progressive's Snapshot program, which can, in fact, force rate hikes.

Onboard video recorders are gaining in popularity -- in fact, DriveCam's sales grew by 87% in 2010. Given the increased availability of the hardware, plummeting costs, and shifting definitions of privacy (thanks in no small part to Twitter, Facebook, Foursquare, et al.), we'd expect to see the trend continue.

But while we agree that monitoring young drivers is important, we have to wonder: what about adults? Or the elderly? Will the trend affect them, too? And should it? Will we learn to stop worrying and love the nanny cam? Check the DriveCam demo clip below, and let us know your thoughts.