I started to work with openhab almost a year ago. I wanted to use the excess energy from our photovoltaic plant in our house and switch some loads. I learned that some usefully hardware like D0 reader over ethernet or RS485 gateway over ethernet or S0 input output or switching simple loads needs quite some hardware. From that first idea of a hardware I ended up in a programmable device that could even be used to build up a simple battery storage system that works autonomously from openhab. The device has a json / tcp/ip interface that can be used to bind the device with openhab. It also includes some examples for mqtt, modbus, sunspec, tcp/ip, udp…
We started a campaign on kickstarter. Maybe somebody is interested in the concept.