I plan to use use my old iPhone 3GS for a tracker-- the find my phone feature works for that and you can buy a $10 Airvoice Wireless card that's good for 90 days- which includes the activation/phone number/100 minutes or about 100mb data. You just have to enable the data. These phones can be had for as little as $30 now. Plugged into one of those 2000mah battery substitute chargers will extend the time between charge to about a week. I just have to plan ahead and build in a good place to hide my phone.