Duolingo

Duolingo ABC (the app) is a phonics app and was amazing for my slow reader. I tried all the phonics apps (well, a lot) and it was the best one. It's also free. We had less success with Duolingo for language learning. Both of my kids got really discouraged when they ran out of hearts or lost their streak and then refused to return to the app. Unfortunately I think if you're going to use this with kids, you should spring for the paid version (which is more forgiving) at the outset. I also agree with the other poster it's not a complete resource for language learning, but I do think it makes a good supplement.