The simplest way to get augmented reality is with a smartphone, QR codes and some software. The software stores data - 3D images, notes, music, whatever - in a database, the QR codes act as identifiers for the data that you can place anywhere visible and the phone reads the codes with its camera and displays whatever data is in the database. You could use it as a way to tag the world, organise virtual note cards, augment ordinary board games, all those things AR is good at. The best part is that there are just two hardware components (printed codes and mobile phones), and they have very high availability.
Mokalus of Borg
PS - The system could be very generic and very useful.
PPS - It would make the physical world machine-readable.