I'm very interested in using Vuforia Chalk for work. In testing it, I found two issues:
The sessions seem to be limited to 3 minutes each. We're willing to pay for a subscription that removes this, but I don't think that's available right now.
We had serious issues with video stuttering, and with audio echo on one side. I seriously doubt this was a hardware problem as we tested an iPhone X and have a network that works fine with other video conferencing tools like Microsoft Teams.