iOS 11 Animated Emoji
Apple is including Animoji in iOS 11, at which will use facial tracking and your voice to let you make a custom emoji that has a facial expression like you do.
This appeared in the iOS 11 GM leak over the weekend and we got a chance to see a monkey, robot, cat and dog emoji changing based on the user's facial expression.
This runs on iOS 11, but it is an iPhone 8 exclusive feature according to 9to5Mac. We expect that like the Apple Watch emoji we saw when it was first introduced that you will be able to send these to any iPhone on iOS 11, but only be able to make them on the new iPhone.