Commercial and military airplanes are generally equipped with every sort of safety device, and frequently the latest and greatest. But the general aviation market is less careful as a group, possibly overlooking some safety devices due to cost. A story in USA Today discusses the reluctance of some pilots to equip their planes with emergency beacons. http://www.usatoday.com/news/nation/2009-01-07-beacon_N.htm.
The particular crash described in the article was one with a “happy” ending because the craft did have a beacon, and a satellite tracked it, and sent help within minutes.
But most small aircraft do not have up-to-date satellite-monitored and tracked beacons, due to cost. The Aircraft Owners and Pilots Association (http://www.aopa.org/) , a nonprofit advocacy group, finds the new-fangled beacons too expensive, with the result that less than 15% of general aviation planes have them.
Older beacons have been required for 30 or so years, following a series of plane disappearances that grabbed headlines in the 1970s and earlier, including the disappearance of Hale Boggs, whose plane crash site in Alaska has never been found. Boggs was a big-deal disappearance, because he was the Majority Leader of the US House of Representatives (his daughter is NPR reporter, Cokie Roberts).
If you are interested in such beacons, places to check might be SARBE for military-spec encrypted beacons (http://www.digitalangel.com/military_sar.aspx) and McMurdo for general aviation and civilian watercraft and yachts (http://www.digitalangel.com/recreational_sar.aspx).