Though difficult, that challenge is easier than it might at first seem. Telemetry is, perhaps, trickier. But at least for the moment, this service is quite pricey. This technique, pioneered by radio amateurs two decades ago, lets two computers share data without a phone or Internet link. The scheme is to break a data file into smaller chunks called packets, add routing information and send them over the airwaves.
Packet radio has another advantage.
Thanks to the visionary work of Bob Bruninga of the U.S. Naval Academy Ground Satellite Station in Annapolis, Md., generating a map on a personal computer that would locate all such drifters in real time would be a straightforward task. With minor modification, additional analog channels become available. So the drifter could, for example, measure water and air temperature, salinity, intensity of sunlight, and battery voltage. For a transmitter, check out your local ham radio outlet-but be prepared to be dazzled. Most offer a smorgasbord of gear with a dizzying array of features.