If your toddler likes music, check out Toca Band for iPhone and iPad. So so cute! It's rare that an app entertains ME to the point of laughing but I enjoyed this app quite a bit!
This app lets you play with 16 different characters that are all playing musical instruments or singing. Each musician you put on the stage adds to your song in a unique way and you can play with them as soloists, exploring their abilities to sing, play, whatever. It's a lot of fun!
Toca Band is made by the same company that makes another one of our favorite childrens' apps, Toca Robot Lab. They're doing good work over there! Toca Band costs $1.99 in the iTunes store.