Reading all the posts about the Kims, PLBs and trip route planning, it occurs to me to bring up APRS, or Automatic Position Reporting System as a trip safety tool. This is an Amateur Radio method of sending short packets of data that usually include GPS position data. This allows people to see where you are on a reasonably continuous basis, depending on the area.

Many operators have this in their cars, boats, planes, where it transmits positions routinely (between 3 and 30 minutes). Usually these packets are received and injected into the internet (via APRS-IS) where they can be viewed worldwide. Internet APRS traffic can be viewed using inexpensive software or for free using the www.findu.com gateway.

Most often APRS is transmitted over VHF to ground stations; however, VHF transmissions can be picked up by several satellites or the International Space Station, and relayed to the APRS-IS. Alternately, APRS packets can be transmitted over long distances over HF to internet gateways.

A simple, transmit only APRS system can be put together for $100 or less, with more complex systems costing more. In many cases, the same equipment can be used with a laptop to send email thru public gateways using a system called Winlink 2000.

http://web.ew.usna.edu/~bruninga/aprs.html
http://www.aprs-is.net/
http://www.findu.com/
http://www.winlink.org/