The iDEN standard is common in North America as well as other parts of the world. AMPS phones contain no built-in modems, and require complicated external hookups you are best to upgrade, or look at one of the other options. It is a packet-switched network, meaning you are always connected as long as your modem is on. CDPD is based on the AMPS system, and has a top speed of 19.2 Kbps. Speed varies with the usage by other users on the system, as well as signal strength, but speeds are generally in the 13 Kbps range.
Cost is on a per-byte basis, although there are unlimited usage plans.
Coverage, while better than other packet-switched options, is smaller than that of mobile phones. CDPD modems are available for all of the Pocket PCs except for the Casio Cassiopeia EM-500. CDPD service is available direct through mobile phone companies, or through a number of resellers, including GoAmerica and OmniSky . Ricochet Ricochet is a new network that just appeared on the scene that allows for transmission speeds of up to 128 Kbps. Ricochet is only available in a few metro areas in the United States, which makes coverage rather sparse, especially if you need connectivity while travelling.