A scary thought ...

My wife's iphone has an app that recognizes music -- it can listen to a song playing on a restaurant's soundtrack and tell you what it is ... even if it's instrumental with no vocals. Amazing.
Google and iphoto have software that recognizes human faces. When you upload photos, your computer now can recognize with fair accuracy who the people are, and then label them accordingly.
Okay ... I'm getting a little concerned. How far away is this scenario: An obsessive, scary individual sees you on t...