DIY tour guide

there's an article in the nytimes about san francisco tour-guiding carts that use a GPS and pre-recorded audio clips to guide you around landmarks and tell you about them. i like the idea. it appeals to the side of me that sometimes prefers not to deal with people and likes to run on my own schedule. i think i'd also want more control over when the thing talked. if i were going to visit an unfamiliar city, i think i'd try it.