I did an in-house development of APIs in which I had done HATEOAS based Framework called Interaction Representation using Interactions, Contexts and Guided flows see below
The concept of Main context and sub-context is driven by User Experience design. The interaction representation framework above has HATEOAS in Guided flows. The main challenge I had was to make the clients HATEOAS compliant. This framework even has code-on-demand in form of xpath and jsonpath to let client know how to construct complex transitions using guided flow.
The framework was successful and adoption among client developers was encouraging. The REST apis was not only targeted for web/mobile apps, but to other UI/UX applications like IVR in call centers.
cheers,
thiyagu