Swiftscales was created by singers - it's a vocal trainer phone or tablet app and simulates sitting at the piano with a vocal coach. Free to download, with in-app purchases. Google Play and iTunes App Store. Some tutorials also available online. See www.swiftscales.com/tutorials.
Vivace is a practise tool both for learning how to read music and improve your music reading skills. Illustrated step-by-step tutorials teach the basics of music theory. Free to download, with in-app purchases. Google Play.