The Crux II BTGPS Receiver is a small unit which incorporates GPS satellite navigation circuitry alongside a Bluetooth chipset. The result is a little box which can add wireless GPS functionality to any device, including a phone or PDA which supports Bluetooth.
I suppose the idea is that you pop the unit into a briefcase or pocket after which it will beam locational information to the PDA as needed. I assume that it needs some sort of software link to make the satellite data readable on the remote device, but even so it looks like quite a clever piece of kit.