Things like, pulling up addresses of buildings you look at, names of people you've met, line on ground for gps, playing board games with people without needing a board or dealing with the rule book (software assisted), see meta information floating around devices (battery level, year, serial number), etc. etc.
The UX of phones is pretty good but it suffers from its form factor. If you could have a UX for the world you can really enable a lot more human abilities in a really intuitive way and you can get closer to something that feels like telepathy.