The backlight is really useful too. Doesn't come on by default - you have to press the num key and the link key at the same time, then it comes on. It also has a timeout so doesn't suck the batteries too much. Comes back on next key you press after the timeout.
Once paired up with the bluetooth dongle, it reconnects automatically so you can power it off completely and hence not have to worry about batteries draining.
It even comes with an (addmitttedly cheap) pouch to keep it in.
I bought mine in the UK for about £45 I think. Expensive for a keyboard but given the very small size and superb use I think it's a bargain. I can even type on it from the living room with my car in the garage! (not that I need it for that of course...). I have a class 2 (100m) dongle so range is very good.
It is slighttly bigger than a credit card and is basically a thumb pad. It is designed for PDAs really as it has a clamp on the back to put it on the bottom of a PDA but works just as well with anything bluetooth.
Thanks for the backlight photo! I just bought one for myself, with the exception of built-in mouse control, I think this thing meets carputer needs almost perfectly. The need for a backlight was the only thing keeping me "wired", now I'll have one less cable to deal with.