Warning: This program writes to a very critical part of the N900. I will take no responsibility whatsoever if it messes up your N900. Use at your own risk.

Warning 2: It's written by an idiot who has little to no knowledge when it comes to C strings...

While I have survived disabling/enabling R&D Mode (and setting flags) using it and rebooting, you never know.

Nokia released libcal-dev in nokia-binaries for Fremantle. This means you can write to the CAL area and modify settings there.

R&D Mode Control is a program that lets you modify the settings pertaining to R&D Mode on the N900 itself.
No binaries because I don't trust the code enough.



Source: http://slexy.org/view/s21xaSNJe0