UPDATE:

Maybe the wiimote has an other file in that directory? or are all controllers js0?

I had the same problem too. If you dont sync up the PS3 controller with the n900 then there wont be a js0 file in that directory. so make sure that the PS3 controller is connected to the n900 correctly before running the script.

If you get the question if you want to connect the ps3 controller when syncing it to the n900 then your bluetooth input in /etc/bluetooth/main.conf is not correctly configured. While connecting you wont see any message.