- Azure Spatial Anchors (iOS, Android, HoloLens, ROS) [1]
- Google Cloud Anchors (iOS, Android) [2]
- Apple Geo Anchors (iOS & not all locations so not ready for use yet) [3]
Integration with these SDKs is pretty easy, and Azure Spatial Anchors and Google Cloud Anchors are production-ready. Minecraft Earth for example used Azure Spatial Anchors for shared multiplayer AR experiences. Infopop is nice, but doesn't have multiplayer or long-term persistence, so not really useful as-is. But wouldn't be surprised if it eventually uses one of these SDKs to provide better multiplayer + shared relocalization. You could probably throw together a rough version of Infopop in a week if sufficiently motivated, ARKit does a lot of the heavy lifting there.
[1]: (https://docs.microsoft.com/en-us/azure/spatial-anchors/overv...)
[2]: (https://developers.google.com/ar/develop/java/cloud-anchors/...)
[3]: (https://developer.apple.com/documentation/arkit/argeoanchor)