Mainly realtime processing. I play video games, and would love to play something like Legend of Zelda and just have the AI going, then ask it "read the menu options as I move between them," and it would speak each menu option as the cursor moves to it. Or when navigating a 3D environment, ask it to describe the surroundings, then ask it to tell me how to get to a place or object, then it guide me to it. That could be useful in real-world scenarios too.

Weird question, but have you ever tried text adventures? It seems like it's inherently the ideal option, if you can get your screen reader going.

Yep, they're nice. There are even online versions.