The most widely-used form of Packet Radio, APRS lets stations transmit periodic position beacons, send messages, and other information and forms a self-organizing Mesh Network with the possibility of propagation by both radios and, less frequently, Internet.
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Most of us carry cell phones with us almost everywhere we go. So much so that we often forget not just the usefulness, but even the joy, of having our own radios. For instance:
WinLink 2000 is generally designed for HF communication, but they have a nice APRS gateway as well, enabling short messages to be sent to and from email accounts from APRS users.
The TH-D72A is a very nice handheld Amateur Radio Transceiver. Among other things, it has an integrated GPS, built-in APRS functionality, full AX.25 Packet Radio TNC, and a USB port (which shows up as a serial device) to a computer – all built in.