I haven't quite started yet, as I'm in the middle of doing a bit of app development. But as I mentioned, I plan on incorporating the procedural lock/key dungeons.
I'm planning on basically making something like Legend of Zelda: Link's Awakening, but with procedurally generated dungeons and overworld.
If that all goes well, I want to add in interesting NPCs that interact in neat and different ways, rather than being generic NPCs that are in any other game.
So hopefully the end product will look something like a procedurally generated Zelda title, with dungeons, characters, and story all being new each time you play.