iPhone: If you rest easier knowing you can peek in the whereabouts of your adventurous teenagers, Whereoscope is an iOS app that turns your family's iPhones into real-time location tools.
Whereoscope is fully automated, so you don't need to rely on your kids remembering to use the application. Once you've installed and set up the application, you specify locations that your kid frequently visits, like the homes of friends and school, and you'll be notified when they come and go from those locations. The location-based notifications are the strongest selling point for Whereoscope; the majority of iPhone tracking tools simply report the location of the phone.
Visit the link below to download a free copy — though they'll be rolling out paid services in the future, they'll be grandfathering in early adopters. Have a family-centric application to share? Let's hear about it in the comments.