Primarily..

Locate aware apps (Android has alot of them). For example, there's one that you can setup so when your near your grocery, it'll remind you what you need to buy. Or if your near a bank that you need to do X.

And there's location aware apps that can modify your volume by location. The closest thing we have at the moment on the n800/n810 is modify it by time (a cron script that adjusts volume by day and time). Ideally like the app, it could be set to vibrate when you get near your classrooms. And automatically pop back to full volume or whatever when your not in those areas.

Evernote!

Locate aware apps are the cause of my jealousy of Android/iPhone =P

Oh and Augmented reality (I'm interested in researching this actually)..

Edit: And if not, then an Android emulation layer. =P