That’s a cool idea. Might be tough to find an input on the arduino if you are implementing an auto z-axis zero.
A chain guide that is a close fit to the sprocket should also work to peel the chain off the sprocket before it wraps.
Man I wish I had AutoCAD at my current job, but here goes:
where the large grey circle would provide a backing for the chain to keep it feeding parallel with the sprocket.
Mind you, I think that @mrfugu’s idea of putting the roller right next to the sprocket works to avoid skipping as well as keep the chain from wrapping. I have been fortunate to only have had the chain start to wrap once while I was right next to it an able to pull it off (this was before I implemented MrFugu’s roller placement), but I am pretty sure that the roller would keep it from wrapping on itself.