Here is my attempt at it:
http://brainsignals.de/users/cristia....1-1_armel.deb

It works like that: open the camera cover and the camera application, and maybe prefocus, such that the autoexposure happens.
Close the camera application (but leave the cover open) and start the Magnus Plus Magnifier.
Find the best distance to the objects/written texts you want to magnify.
The focus is fixed, to the closest distance the camera on N900 seems capable of.

The step with using the phone camera for autoexposure is optional, you should only do it if what you get on the screen is too dark or overexposed.

Have fun with it, of course I would love to get some feedback.