I love these kinds of grid step sequencers and have had an obsession with them since I saw a Monome as a teenager. I tried to make my own capacitive touch hardware once that could work as one. Eventually I just settled on writing a MIDI Node.js one which works with a Novation Launchpad [1].

This one is really well done and gives me some ideas. Would be cool if it took advantage of bigger screens.

[1]: https://github.com/kasbah/launch-step