I've released a new Sudoku game for Android, MySudoku, available for free at Android Market.
It started as a toy project for learning Android, reusing code from a very simple command line brute-force solver I did in 2005. Having no real experience with the pencil & paper Sudoku, I then thought singles were all there was about it, and started coding.
When writing the step-by-step solver for the hint engine, I discovered several excellent sudoku web resources (such as this forum), got sucked in and implemented a basic set of techniques, enough for most mainstream puzzles (naked/hidden singles/pairs/triples, locked candidates, X-wings inc. finned/sashimi, Y-wings, nice loops & forcing chains). The original brute-force solver is also included. Provided puzzles were generated with QQWing, and you can type them from elsewhere, too.
All feedback is welcome. Thanks!
http://twitter.com/#!/MySudoku