I thought this was a neat idea too and was hoping that with a bit BT Python fu I could make it happen. I wrote to Albert Huang, the developer of PyBluez, about the idea. This is what he said:

"Implementing the HID specification is a nightmare, I do not recommend
it. However, you also do not need PyBluez to control your nokia
device. I am not an expert on HID, so you will find better advice by
searching the bluez mailing lists and wiki. If you want to hook into
the keyboard events, then use a higher level layer like those
provided by X."

I find that Putty + WinSCP on my PC and ssh on the tablet meets most of my needs for a keyboard. You should be able to configure your lap-top to connect directly to your tablet over wifi. WinSCP is really nice, recommended.

I have not tried it, but somebody has already mentioned Synergy. Again, you would need (I think) a wifi connection. The issue with Synergy is seeing the mouse pointer on the tablet so that you know where to type. I recall somebody saying they had solved this problem (search...) but then Amazon had the iGo keyboards on special at $29.99 so I bought one of those for the occasions when I can't use Putty.

Another quite viable alternative is to use a VNC server on your tablet and a VNC client on your laptop.

Final idea if you have an old 770 available:
http://internettabletmania.wordpress...he-nokia-n800/