With this Raspberry Pi HAT you can extend your Raspberry Pi with functions for smart metering. The HAT provides an M-Bus master to which other M-Bus devices such as electricity, water or gas meters (with the appropriate interface) can be connected directly.
With libmbus, powerful C++ software is available for the Raspberry Pi, which can be used with the M-BUS HAT. If you prefer Python take a look to the pyMeterBus project.
This HAT is also available at ThePiHut.com.