[Myrddin]

Batteries and antennas with sufficient capture area
for GPS put a lower bound on size. A flat “polapulse”
battery as supplied with early Polaroid film cartridges
are fairly compact. A ceramic disk antenna is
about 1.25 inches square and 1/8” thick. A common
surface mount GPS chip is about 1” square. The
collection of parts rarely ends up smaller than a deck
of cards. There is also the matter of space for a
transmitter to send the location to a monitoring
receiver. Frankly, something like a Motorola Droid
has nearly an optimal mix of parts.

[mad_as_he$$]

Yup, a droid tied into the vehicle power system and you can access the position for weeks or months. Way more concealable than the current Fed stuff. For many years now the chips have been very small, it is all the stuff needed to make them work and talk to the outside world that takes up space. I also like it in the movies when they are 100 miles from anywhere and the quarter size unit is sending data back to them. lol...