A month ago at Build 2015, Microsoft officially revealed its "How-Old.net" website, which uses new face recognition APIs to guess the age of a person based on a photo. Now that feature is being slowly rolled out onto the company's Bing image search engine.
Microsoft has yet to announce this new feature, but it is definitely available for at least some Bing users. Basically, they can search for a person's image in Bing and then a logo with the words "#HowOldRobot" should appear on the right side of the photo. Clicking on the logo brings up the "How Old" age guess. A message that pops up after this happens states, "Sorry if we didn't get it quite right, we're still improving this feature."
Again, this feature is still rolling out so it may not be available worldwide for all Bing users yet. In the meantime the "How-Old.net" website is still up and running, and it's also available as a Windows Phone app.