from the TechZone review:

DX1 Keys are assigned to match a single keyboard key, such as the letter "a", or to perform a more complex macro containing a series of keystrokes. Keys are also "application" aware, so as the user changes from, say, email to Photoshop, Keys automatically change to the macros for Photoshop. Even though Keys contain advanced electronics, they have no batteries and no wires; they communicate wirelessly with the DX1 pad. Ergodex’ "Molecular Velcro", an inexhaustible adhesive, allows Keys to adhere tightly on the Pad. A slight twist loosens a Key so it can be moved or micro-positioned for optimal placement.

This one is also nice: http://www.artlebedev.com/everything/optimus/ — you can create a custom mapping for the keys and keys appearance (LEDs on top of the keys) — somehow nicer than Xmodmap ;-)