GPS Art

A briefcase + GPS + many batteries + DHL + the World = self portrait

http://biggestdrawingintheworld.com/drawing.aspx

Population movement tracking in malls

Using people's phones as a way to track movements.

http://technology.timesonline.co.uk/tol/news/tech_and_web/article3945496.ece

Here the IMEI numbers unique to each phone are determined from shoppers so that the number of shoppers, country the phone is registered, and length of time spent in the mall can be stored. The trends can be used to extend shopping hours, or change the language of signs if it's found one nation is well represented in a shopping mall.