for my lego creations, ive hand made all of my controls.
i just get a bunch of resistors and arrange them so a switch or button runs a current with different voltage. (the lego RCX senses different voltages) and can use that as input. resistors you can find in any kind of old electronic device so its cheap. actually, free. just go aound saying youll take anything electrical that they dont need. youll be suprised how much junk people have..
and also not that its really probable for awhile, but controlling a robot with a touch screen would be COOL!!!.
have a field on the screen and touch a point on the screen and the robot moves to there. crab drive might be useful for this. omnis too.
oh the possibilities!