I made Nipples for use in my performances and VJ gigs. I needed something which offers fine grained control, better than the usual 127 values MIDI controllers offer. This is especially important when controlling animations which rely on feedback loops.
The three nipple knobs use high resolution magnetic encoders from AMS (AS5047D). These could be much lower resolution but it is what i had on hand when i made it. The micro-controller interprets the signal from the encoders differently depending on the speed of rotation, which allows very fine grained control if they are moved slowly. It sends the values as 14bit CC messages that give a resolution of 16383 instead of 127.