http://www.geocaching.com/. It is the most fun your kids will ever have with a cell phone! All you need is a smart phone or a handheld GPS device (the kind used for hiking) and you're on your way. All over the world, geocachers hide boxes and then upload the coordinates to geocaching.com. All you have to do is access their app on your smart phone (or download the coordinates into your handheld GPS). It's free (minus the cost of the app) and it gets you outside on a treasure hunt with your whole family. My kids absolutely love it! The best part is, most of the larger caches contain small trinkets or prizes for kids to find. You simply leave a new prize and choose one to take with you. There are even travel bugs that get moved from cache to cache, and you can look up and see where all they've been. I HIGHLY encourage you to get your kids involved today.