I know this kind of stuff is getting small, but built into a 2GB SD card? That's kind of insane. I'm sure it's missing a lot of logic circuitry or something, relying on the (no doubt Windows-only) software to do everything for it. Like a winmodem from the days of yore.
Even better, why bother with wi-fi (which is meant for relatively long distances and meant as a network transmission medium), and have this device work as a Bluetooth device, as Bluetooth is designed specifically for wireless high capacity storage media at short distances (under 15-20 feet)?
If the device has the latest rev of the Bluetooth spec, once paired, its very secure.