One of the more impressive demonstrations of augmented reality application programming centers around facial recognition. From security applications that can recognize a friendly person vs. a known threat, to social applications that scan the crowd for your Facebook friends, to retail applications that allow you to try on sunglasses or different hairstyles, facial AR is amazing.
Traditionally, the challenge with facial-recognition programming is the amount of resources required by the machine to process the images in real time. This, naturally, makes it very difficult to target mobile devices. This is why we see most facial-recognition algorithms running through a browser or installable program.