One of my favorite features about the Apple Watch is the ability to quickly view and respond to text messages on the watch. In addition to being able to pre-program in a few of my favorite "canned replies" the Apple Watch will analyze the text of the message you just received and offer a few additional likely response based on the context of the message.
Turns out the Apple Watch is a little smarter than I thought. Today is my brother's birthday. Apple Watch knows this because his birthday information appears on his contact card (and thus appears on my calendar). Today when I received a text message from him, at the top of the suggested replies was "Happy Birthday!" How cool is that?