Control.com - Nerds in Control

I have planned to do a project that would generate the sheet music automatically while playing a piano. The problem i have is to detect the notes played by the left hand from the right hand. My lecturer suggested i use some kind of sensors attached to a wristband which i can wear on my left hand so that every time i play, the sensors would detect how many fingers are being used to play. I'm not allowed to attach anything on my fingers as it would affect the playing.
Does anyone know if such wristbands are available? or anything that might help me out with this problem?