First of all thank you very much for the reply.
To be more specific I would like to be able to register both knocking and scratching. The ability to locate the movement on the wall is also important.
If it can locate multiple locations at once even better. The more precise the better as well. I got a reply from IcubeX and they offered me a device for about 20 Euros. If I now know which exact Arduino component needs to be bought I can then proceed in rounding up all these elements and actually starting my work.
This video is actually quite close to my idea but this is way more elaborate, has the visual aspect and it also incites to move much faster.
IcubeX offer me this: http://icubex.com/bang
I would use Processing, but I have literally ZERO previous knowledge about programming and such things, although I am ready to learn at least to achieve this program I am intending to do.
Basically it is about playing the sounds on the surface of the wall, measured maybe only be velocity ( strength applied when hitting or scratching the wall ) and location which determines the midi note being played. The area of the note being played is also quite important to be able to achieve the maximum amount of midi notes on one wall.
Again thank you for your help, hope that maybe other have some input as well, I really need as much help as possible on this. Also if people know good forums about PROCESSING in relation to ABLETON LIVE with Promidi and ARDUINO that would be amazing. I really need as much help on this as possible as I admit being an absolute beginner concerning programing and such things.