Are there mobile chess tutoring/training apps for Android or iPhone? I'm looking for a Chess tutoring/teaching app that I can dip in and out of on my phone. At the moment I use Shredder Chess to practice when on the move (which basically involves repeating the puzzles over and over) but I was looking for some sort of app which has structured lessons on openings, defenses etc. and explains the positions in depth like Chess Mentor does. 

Does anyone know if this type of app exists?
Here are my Chess apps for Android:

iChess — lots of chess tactics to solve, all offline. You can also load your own PGN or purchase recent tactics based on openings, or from recent games.

Chess Book Study — a very innovative app that shows a board and an eBook in the same screen. It makes it easy to study chess books. You can even dictate and the moves are made on the board.

Analyze This — analyze a position with two engines, simultaneously!