Apple released shared AR experiences a while back along with their ARKit2. Here's a video they released to demo the feature
It's powerful. And it's supposed to work peer-to-peer meaning no need for a central server to organize the shared experiences.
I think the feature can be a great way to demo and interact with some cool physics. Here's a website that lets you play around with how gravity works with different masses and velocities. Shared AR can do something similar in a classroom, in 3D, in realtime and in a collaborative setting.
What other applications can you think of? Lmk in your comments