What are some alternatives?
When comparing Simply Piano and Jameasy for Violin, you can also consider the following products
Flowkey - The easiest way to learn piano with your iPhone or iPad
Yousician - An interactive guitar-learning app.
Pianu - Learn to play the piano in your browser.
Touch Pianist - Play piano like a pro without playing piano.
alphaTab - alphaTab is a cross platform music notation and guitar tablature rendering library.
Playground Sessions - Online piano learning game.