JoyTunes has developed a couple of wonderful apps to help piano students. Piano Maestro and Piano Dust Buster are both super fun and educational. You won't even feel like you are practicing. My father-in-law even tried Piano Maestro and didn't want to stop playing it! We use Piano Maestro in the studio to help students with their sight-reading skills.
We use the Note Rush app in the studio to help students learn their notes. It is a great app!