A detailed tutorial on how to make your own APRS iGate (Automatic Packet Reporting System) from Andrew Milluzzi:
With the super cheap embedded Linux platforms (Raspi, Beaglebone, etc.) and cheap TV dongles, it is really easy to make your own APRS iGate, just like the one in the photo above. This tutorial will give you the steps to get going with an APRS iGate. What is APRS you ask?
APRS stands for Automatic Packet Reporting System. It is a 1200 baud RF (mainly ham radio) packet system commonly used to record telemetry. Sometimes it is fun to log a trip or track a robot. APRS is a great tool for these sorts of problems. In the USA, APRS is commonly used on 144.39 MHz. It can be used between radios directly or can be used to log on the internet (via websites such as APRS.fi) via an internet gateway or iGate.
Details at Milluzzi Labs.