It really depends on what you mean by “data”. You can create templates, scripts, services and such that would allow the data to be shared, but I’m not sure what else you are looking for beyond that.
For example, I have a Shelly Wall Display with a thermostat and I want to use the measured values, such as temperature and humidity, as well as the set temperature in Homematic to control a heating actuator there.
So far, I read these values into Homematic via an http request.
Ahhhh, I see what you mean. Doesn’t homematic expose entities and services? You should be able to use a service to communicate information from your Shelly entities to your Homematic entities and vice-versa.
It sound like you are trying to feed a sensor value into the honematic ecosystem and then let that system react to the sensor value.
I am not sure that is possible as such.
What is possible is to let HA react to the sensor value and then use service calls to get the wanted action in honematic