Location Groups:

-I might shop at 3 different grocery stores. Let me group them together and nickname them, so that when I arrive at any one of the locations, I am reminded of a task.

Traveling Salesman Tasks:

-Track my path taking habits. Bring up traffic data and the next time I'm headed on a path toward a location that's in my history, show me how bad traffic is along my path.

I have a ton more ideas but I suggest you stay simple like Dropbox. Personally, I think taskave is a niche tool in my GTD workflow. That's okay though. It fits those tasks that don't necessarily fit into a particular project or context (in the GTD sense of those words). I always bundle those under "miscellaneous" or "errands" and it gets old very fast. Keep it simple. You don't have to keep on adding features. Even the ones I mentioned above might be pushing it.