This is what the BAFA states:
Acquisition costs (replacement and new acquisition)
The implementation of electronic systems for operational optimization, increasing energy efficiency, and improving the grid compatibility of the funded heating technology systems is supported. In principle, both components of measurement, control, and regulation technology (MSR) as well as building automation technology up to comprehensive building management and energy management systems can be considered, provided they also serve the operational and consumption optimization of a fundable heat generator.
Sensors, actuators, data loggers (e.g., also electricity and heat quantity measurements)
digital/electronic radiator thermostats / room thermostats,
displays or user interfaces for displaying current data relevant to energy consumption,
digital/electronic systems for capturing and evaluating energy flows, energy consumption, and energy costs
digital/electronic systems for energetic operational and consumption optimization or for improving the grid compatibility of the technical systems of the building ("Smart Home")
building automation systems including field technology, building management technology, energy management systems
b. Assembly and installation
including the required technical work and materials