Continuing with the crazy product ideas...
What if there was something, like a mobile app, when pointed at someone can give me information about that person? This would be scary but lets keep aside the privacy issues aside for a moment. It would be like an intelligent visual address book which recognize people in real time and gives me information using "Augmented reality".
Say if Google comes up with this mobile app, when pointed at someone, will capture the image of the person and do an image search and find out who the person is. Google would also know if that person has a Google account and hence can show me some non sensitive profile information about him/her to me.
Something close to my idea has already been prototyped by Pranav Mistry of MIT which is demoed in this video.