More generally there is the larger scale wish for what I would call 'Universal Human Interface Device' messages, which would encompass not just mice and keyboards, but also midi controllers and other control surfaces. The idea with these is that, for example, the knobs on a midi controller should be able to control e.g. the width of a pen in Gimp. Ultimately such devices, like mice and keyboards, need to be very dumb. Basically they tell the machine what happened: endless rotary 4 moved clockwise by 5; slider 3 was moved to position 10; button 3 was pressed; button 7 was pressed with velocity 45; button 7 registered a pressure change, new pressure is 43. As raw as possible, and make the rest software defined. Likewise for readouts, again make them as dumb and software defined as possible: a vu meter should respond to values sent to it. Mini displays should be possible to write to. (There are possible performance issues with this last one, but surely Usb is fast enough?)