Ok, I asked because the ST Schema Connector can help you in this case but you need to consider the following:
- The measures and commands accepted by your device:
a. I guess you know how to parse the JSON received (which value corresponds to which measure), so, is there a standard capability you can use to display each one of them?, so, is there a standard capability you can use to display each of them? eg. Temperature Measurement, Heating Setpoint.
b. If it has a manufacturer-specific capability or none of the standard ones works as you want, you can create a custom capability. - As the external device is reached through an open API, you would need to create scheduled queries to get its current state (that could be done by a SmartApp or using the Connector’s State callbacks).