APRS: Automatic Packet/Position Reporting System
Some Ham Operators choose to "beacon" their vehicle, bicycle, or even their own locations, using the APRS System.
In North America, the most commonly-used frequency is 144.390 MHz Simplex.
There are many "works out of the box" solutions, including Byonics.com; I use 2 of their "MT-AIO" units, which can be carried easily in a back-pack, or installed in a vehicle; they will run off of 8 AA batteries, or from external 12-volts DC.
