APRS was developed by Bob Bruninga, WB4APR, to track mobile GPS stations with two-way radio.
APRS is turning into the most exciting mode of Amateur Radio.
By using APRS one can track cars, search and rescue teams, parade floats, ships and even airplanes.
You don't even need a radio, just an Internet connection. If you do have a two meter (144.390 MHz) radio with a TNC, you can easily join the fun as well. The
San Diego Repeater Association maintains an APRS system at the Mount Laguna ham repeater site.
(Links are inBlue)
San Diego Repeater Association