The company nD-enerserve GmbH from Hannover / Germany has launched a Kickstarter campaign to transform the Raspberry Pi into a smart meter.
The SmartPi called expansion module extends the Raspberry Pi with interfaces to measure current and voltage.
Current is measured contactless via split core current transformer that are clamped to each phase.
This has the advantage that no modifications need to be made to the electrical distribution system.
In addition the voltages on all three phases can be measured to determine the power exactly. Also, a determination of the phase relationship between current and voltage is possible. The measurement of the energy flow turns the SmartPi into a bidirectional counter with logging and remote readout function.
More meaningful values ​​are active power, reactive power, energy, frequency and power factor (cos phi).
The necessary software is written in Python and is under an open source license. So that SmartPi module can be used in private, also commercial, projects.

More information can be found at:
http://www.emanager.eu/de/produkte/smartpi-leistungsmessmodul-fuer-den-raspberry-pi
or on Kickstarter at:
https://www.kickstarter.com/projects/1240982104/smartpi-turn-your-raspberry-pi-into-a-smartmeter

The nD enerserve GmbH develops and manufactures energy management systems to optimize the own-consumption. They also develops and manufactures control technology for smart homes, Industrie and Internet Of Things (IoT).
Products of nD-enerserve GmbH allows the connection of energy producers and energy consumers.
Sensors (temperature, analog, digital, switches) and actuators from different manufacturers can be connected via standardized interfaces.
Based on the Linux operating system products offer a high degree of reliability and safety.
Another field are customized solutions based on existing products and systems. By the modular design of the products, development processes can be kept very short and inexpensive.