The energy-metering module is based on the Cirrus CS5463, with a shunt resistor providing the AC load current signal and a voltage divider providing the load voltage signal. But I might swap it over for the Atmel/Microchip ATM90E26 since it's substantially cheaper. The power data is read out by the MCU/wireless board via the SPI interface.

A pair of terminal blocks provide the line and neutral connections to both the AC supply and the load, and an offline switcher provides power to the system, just like the wall switch board. A 10A relay switches power to the load, with the logic-level relay drive passed down from the MCU, and 3.3V power supplied to the microcontroller board.