Since I’m part of the team which developed the HomeMatic component for HASS: @mrMuppet is right, it’s used to access the system variables of the CCU / Homegear. Furthermore it also has an attribute for the “Systemmeldungen”. So when there’s been a communication error or the case of a shutter contact has been opened (sabotage detection), then HASS can read that with a Template Sensor. Although in this case just the sum, not the individual messages. But at least this is enough to get you notified is something is wrong with your system.