What are some alternatives?
When comparing Touch Pianist and Simply Piano, you can also consider the following products
Pianu - Learn to play the piano in your browser.
Flowkey - The easiest way to learn piano with your iPhone or iPad
Type Drummer - Drum by typing
Yousician - An interactive guitar-learning app.
lightnote - An interactive site to learn the basics of music theory 🎶
Keezy Drummer - Make a beat in seconds