iPaq

The device has extension ports that allow PCMCIA and Compact Flash. These adapters are in the $50 range. There are wireless modems available but they're fairly pricey : ~$350 for the modem, $50.month for the service. All in all it looks pretty good. Schematics/specs open, Linux/X already ported. The specs are reasonable ( unlike Palm ) it's a 206MHz ARM9, USB, Audio, 320x240x12bit display, 16Mb FLASH, 32Mb DRAM if I recall correctly. Throw in a 512Mb IBM microdrive, CFS, it's not bad. Looks like the most secure option to me. Gateway SW over USB ( even for M$ OS ) shouldn't be too tough. I guess you could trust an M$ machine to handle already encrypted packets.