i have not chosen the sensor at the moment as i am confused on which one to get though i am thinking to get this one:
and this is the motor i am going to use: http://www.maplin.co.uk/p/motors-n72ch (THE SMALL ONE) it is 3.5v
the arduino was initially supposed to turn on speakers to play something from a mp3 as well but thats really complicated and i will not be able to do that!