I have just gotten a NIBE heat pump with a connection to the NIBE Uplink web service, which has an API.
I also have an existing Siemens climate system with sensors and radiator motors in each room from which my Rpi3 gets info via a connected KNX-RF antenna. I need to send any heat demand or wanted temperature from the climate system to the NIBE Uplink APi somehow. I could do it via Node-RED->IFTT->NIBE Uplink, but would prefer to leave out IFTTT if I can. Also by directly connecting to the API I could also selectively read data from the heat pump.
About API (free to register and read documentation): https://api.nibeuplink.com/Home/About