It is not really feasible at this time but still, wouldn't it be interesting. A phone app that uses GPS to play TNN in real life. Place a mine at a store you don't like, add a DP card to a nice restaurant. Telling your friend you can't leave your apartment building until you solve this puzzle crate.

After this would be a real-world HUD. Then the Matrix.

Sounds... pretty neat, actually. Though someone would need to figure out how to get the portals working. ;D

Teleportation of course.
Perhaps you could have portals link to websites. A coffee shop links to the history of coffee or something.