Amateur radio has a system called APRS -- Automatic Packet (formerly Position) Reporting System[1]. It originated in the 1980s and it's basically Twitter. I'm n

Amateur radio has a system called APRS -- Automatic Packet (formerly Position) Reporting System[1]. It originated in the 1980s and it's basically Twitter. I'm not kidding. It broadcasts small packets to everyone in range. Those packets commonly include things like position reports, weather reports, and yes, short arbitrary messages. Receivers can, of course, filter on whatever they want. I can see the firehose of everything going on for miles around me, or just carry on an IM-like conversation with somebody. Repeaters can spread messages over a wider area, or even upload them to the internet[2]. Usually it runs on licensed 2-meter frequencies, or a variant on HF, and it only operates at 1200bps, but in principle it can be generalized to faster data rates, frequency hopping, etc.. Mass-produced equipment designed specifically for this sort of thing could be relatively cheap. The trick is making everybody want one when they already have smartphones. [1] http://en.wikipedia.org/wiki/Automatic_Packet_Reporting_System http://en.wikipedia.org/wiki/Automatic_Packet_Reporting_Syst... [2] http://aprs.fi/ http://aprs.fi/