iPhone Case With Slide-On Smart Battery
If you exercise outdoors, then you know how essential having your iPhone can be to your safety. The GPS can prevent you from getting lost, and if you get hurt, help is just a quick phone call away.
Running out of juice is just not an option, and since you can't exactly plug into the nearest tree, check out the Slim iPhone Case With Removable Smart Battery ($90) made by Third Rail. Use the slim case alone to protect your phone, and when you need extra battery life, just slide the superthin battery pack onto the back of the case. If you need extra juice for even longer trips, you can purchase additional smart batteries ($60). Before heading out, you can charge your phone and the battery at the same time with the micro USB cord included, and you're ready to go.