There is now a way to wake your Nokia N900 from sleep by simply shaking it. Be careful though because you might drop your phone from overshaking it.
All you have to do is download a simple python script here and upload it to “/MyDocs/Scripts” through WinScp. Fire Xterm, proceed to the folder where you uploaded the script and execute it with this command “python shake.py” without the quotation marks. The application can recognize your shakes as long as the card terminal is open. Terminate the terminal and it will also close the python app. It should appear like this in Xterm:
This python app was developed as a response to a brainstorm discussion in Maemo Forums. I really hope that someone can develop an applet to turn this application on/off.
Please bear in mind though that this application eats a lot of resources thus it can drain your battery.
Source: Niklaksen Blogi