For our native iOS App written in Swift we have implemented a 360° viewer for images of spherical cameras in SceneKit based on CTPanoramaView. It's basically a sphere, that the image is mapped on and the camera is fixed in the middle so you can look around.
The tool we build is for real-estate companies and they use it to create virtual tours.
So now we want to implement the possibility to add "hotspots" in this viewer. Basically it's about adding a flat graphic in the 3D space, that can be dragged around with a fixed distance to the camera. This very isolated feature would be your job :)
For questions please don't hesitate to ask.