I found it super helpful, and I believe it's based on technology originally developed for teaching guitar.
Not sure if it's open for programming your own songs in or not, and much of the library is behind a paywall.
Also my experience with using those things is that you would be better off spending the time to learn sheet music because once you get past twinkle twinkle little star, the falling note style videos don't work. You can't keep up with them live and paused they only show you the very short term future.
Having said that, an e-ink reader that could read visual cues would be awesome, but I feel it could be very frustrating unless it was incredibly smart. Maybe some kind of blink gestures might be useful.
Also, eink screens are nice to look at but so expensive for non-kindle sizes.
chucking the ipad because of that is like chucking the baby out with the bathwater because the bathwater got cold. The baby still has value. you just replace the water.