Microsoft Online's latest inclusion is the "Microsoft How Old" app. As the name suggests, the app simply tells you how old you look. Previously available on web at http://how-old.net , the service is now finally available on your Windows Phone device.
You upload a picture, and let the app predict your age and gender with the help of newly released Face-detection API's powered by Microsoft Azure.
Nevertheless, the app showcases one very important aspect, Microsoft Azure Machine Learning. More about it here.