Glassface is an app that lets you add a friend on social networks by looking at their face with Google Glass.
Say, for example, that you just met some cool people at a #hackerfest and you want too add them on Facebook. In a natural conversation, just say "Ok Glass, add this person on the web." Your Google Glass will take a picture of your new acquaintance and upload it to the cloud for facial recognition, then display the matched profile to you for confirmation. With respect to privacy, the service is limited to users that opt-in to link their Facebook, Twitter, and Google+ accounts.