Talking Street is a cellphone service for providing a tour of a city by users calling a number with their cellphone as they travel the route (only in NYC and Boston - stoopid city dwellers). From their website:

It's as simple to use as an audio guide in a museum'”except you use your own cell-phone. Just choose a stop, call the number, and enjoy an audio segment about the place where you're standing.

Heck, look at the narrators: Sigourney Weaver, Jerry Stiller, and Steven Tyler. There's a motley crew.

The service is a pretty ingenious way to offer tours to anyone, anytime. Could also provide a single point of service for different customer interests: history, culture, current events/life, etc.

It would also be great to sign-up for a general service which sent you SMS/email messages when you arrived in an interesting area, and not just when you were taking a specific tour. "The building you are now walking by served as the city's original firehouse in 1758..."

However, I guess that wouldn't be 'Talking Street', but 'Texting Street'.