Shelly products can be addressed via REST-Api using the HTTP commands (requests) from Homematic and the response can be further processed.
This works with the Homematic control units CCU2 and CCU3, also with the kit Charly, Raspberrymatic and all offshoots.
The only exception is the homematic IP access point. At this one no Shelly products can be connected.
On the Homematic units the add-on CUxD must be installed, the devices are emulated with it.
Here is an overview of already successfully coupled devices. With the links you get to the detailed description. (currently only in german language)