Just found this on a blog, glad to see that other people are contemplating similar issues!
Toronto Urban Etiquette Project (Yay T.O!)
SNL Headz Up App
Notice how many people are looking down, some at maps, many at mobile phones.
( Pics taken by me April 2012)
Taken by me in Times Square, April 2012
Problem or solution?
Coming Soon: iPhone app for texting while talking to another human being.
Image by Brecht Vandenbroucke