If you're looking for a way to build a graphical user interface on your own, you may want to take a look at HousePanel...
If you're really just trying to create a RESTful API to access data from Hubitat, you may want to take a look at Hubitat's built-in MAKER API app. If you only want to collect data, and not change anything, Hubitat unofficially supports an Events webSocket.
Lots of possibilities... Just need to understand your requirements a little more and the community will be glad to help.
