The UberTracker is an accessible way for just about anybody to add a GPS tracking system to whatever they want. It'll send GPS tracking updates to an email address or web server by way of a cellular antenna. You'll need a power source for the UberTracker — a 7-volt battery or a 12-volt automobile power source will do — though you won't have to install any software or slug through confusing setups. The UberTracker has a simple menu system and can even send updates that are Google Maps compatible so you can visually keep tabs on what you're tracking.
The UberTracker itself is $450, though if you want it to, y'know, actually do some uber tracking, you'll need a working SIM card with a plan that preferably includes data for online access. In other words, you're pretty much looking at a second high-end cell phone.