Those plug-in GPS dongles work great but often leave you with a drained battery and don’t help you at all with mapping. The Trimble Outdoors TopoCharger will help you with all of those things! The TopoCharger is a case with a battery pack that can be recharged using the supplied micro-USB cable. The internal 1460mAh lithium-polymer battery doubles the life of your iPhone 4/4S or 5. Your purchase comes with the Trimble Outdoors Navigation GPS app. The TopoCharger holds the maps of your choice on the Map Card storing them to the device with no worry of using up your precious iPhone memory. With your maps now loaded, you no longer require a cell signal to navigate trails, campsites, destinations or just about anywhere you want to go. Works great for Geocachers as well. 18 zoom levels (1:250K to 1:24K) provide navigation down to 20-foot contours. If you want to purchase additional maps, simply buy another Map Card. The TopoCharger is due to be released this coming March. Learn more about it and get on the notification list here.