http://www.hw-server.com/test/sld_hws.html Take a look at the DIMM modules.
Looks like a good candidate for a battery-powered portable VoIP/GSM encrypted cellphone. Add a GPRS modem or a cellphone (or, for landline version, a modem), a small display/keyboard, and eg. SpeakFreely with suitable session key handshake, stir, serve warm. Does it look like an usable way to have open and reasonably cheap ($160+cellphone+some parts around) portable secure telephone platform? Does anybody here have any experience with embedded computer hardware, who could confirm or deny this kind of hardware as bearing hope for this application?
