Playing a violin requires far more finesse than just dragging a bow across its strings. There are subtle nuances in motion, pressure, and speed required that take years to master. Or, you can wait for Dylan Menzies to perfect his easy-to-play optical O-Bow and just skip all the practice and rehearsals.
Instead of strings, the instrument is essentially a smooth copper cylinder with a dented groove that holds the bow as it's dragged across. At the bottom of that groove is an illuminated optical sensor that tracks the bow's speed, angle, and position, allowing different notes to be played, including the vibrato effect stringed instruments are known for.
On the backend there's of course custom software that manipulates the violin samples in real time to match what's being played, but like with a MIDI keyboard the O-Bow could also be used as an interface for a whole symphony of virtual instruments. And while it's just a research project at the moment, Menzies does hope to one day commercialize the O-Bow and presumably save young musicians from hours of tortuous practice.