had totally forgotten about this post, getting back to it in case someone finds it by googling.
The definitive solution would have been writing something in C or C++ using the linux/input.h library. I was even given a good stub here:
However, due my lack of C experience, it was way easier for me to use supercollider - it has a GeneralHID class which makes making midi from any HID (included my device) a breeze. Here's some example code, rather old and convoluted but should be easy to hack:
(also go through the GeneralHID help file in supercollider)
In the meantime I've come to know that also puredata has something similar to GeneralHID... I chose supercollider only because I allready knew it a little - if you're gonna learn this from scratch only to do this maybe with puredata you'll be up faster, from what I hear it's easier for simple things like this.