If you go to Bing and search for images of people, you may see a little overlay on top of the image, after you click on the image thumbnail that says “#HowOldRobot, see age guesses.” If you click it, the image will be processed by Bing’s age tools and tell you how old it thinks the person is in that image.
Here is a picture of the feature before you click on it:
You can see the feature on the top right of the image.
This is designed by Bing, hosted at how-old.net. Bing is experimenting with trying this on Bing Image search.
I should note, I tried replicating this both several browsers and operating systems. It only worked for me using a Windows machine on Internet Explorer.
Venture Beat spotted this feature by way of a tweet from @Fusionfan45.
The feature itself is not always that accurate, as you can see.
Postscript: Bing has officially announced this on their blog now.