monline

There's an episode on National Geographic's Explorer show titled "Science of Surveillance". They said that there're no implantable GPS devices yet. Do they really think we'd believe that? There're already a large number of implantable devices (eg. pacemakers) that can work for years with a lithium battery. Why not a GPS device as well?

I've found the following info by searching for the terms "pacemaker battery life":
"Modern pacemakers have sophisticated programming capabilities and are extremely compact. The smallest weigh less than 13 grams (under half an ounce) and are the size of two stacked silver dollars. The actual pacing device contains a pulse generator, circuitry programmed to monitor heart rate and deliver stimulation, and a lithiumiodide battery. Battery life typically ranges from seven to 15 years, depending on the number of leads the pacemaker is configured with and how much energy the pacemaker uses."

Now for the size and power consumption of GPS chips check the following by Motorola:
"Motorola today launched its FS Oncore module, a breakthrough miniature Global Positioning System (GPS) product. Smaller than a dime at 200 square millimeters, it is used for adding accurate location sensing to virtually any portable electronics product.
(...)
The FS Oncore module consumes an average of 70mW while providing one position fix per second. Power consumption is minimized by the on-board power management features, which will only power on the TCXO while GPS measurements are active. This module also can be placed in standby via software commands, thus reducing current consumption to less than 15µA."

OK, I admit that putting together these requires a bit of abstraction. The above GPS module was developed for use with cellulars and not autonomous operation. This GPS module is only a receiver, so not ready for tracking. And there're a number of other things to be worked out.

However I doubt that the most high-tech developments in this area have not reached the point yet, where a GPS transmitter could be implanted into an individual. Military, intelligence agencies, etc. have always had a reputation of possessing technology years beyond civil developments. I bet there're already implantable GPS modules out there. The applications of such devices would be simply too advantageous for not having focused on their development long ago.