The BEST

This is the best I have seen for learning. As the developer has noted, if you are serious about learning, this is the App for it. No unnecessary fancy graphics, sound or other distractions. Very businesslike. But customizable with progressive learning, not just showing some notes randomly. Good job.

If the developer can add MIDI also so that it can be used with a real piano/keyboard, this can be a paid App.

RVApps about Notevision - Sight Reading