An article from Technology Review News details a project at the University of Rochester that involves using passive RFID tags embedded in a facility as a trigger for digital audio or CD- based guidance.

The idea is similar to the ones used in museums that have guided tours that require you to start and stop a CD or cassette tape when passing numbered markers.

The key innovation here is that by using RFID technology, the markers are self-activating and thus can be used not only for applications such as tours for sighted people but also as audio guides for the visually impaired, since the user doesn't need to see to activate the audio.