Entirely electronic four quadrant multiplier will let a digital(or analog) multimeter measure real watts without any additional digital circuitry or software embedded firmware magic (cheap for the OEM)
The multimeter only acts as a panel meter readout. The four quadrant multiplier analog wattage converter front end can be built into a multimeter sized enclosure.
Digital processing does not always rule (Or, what makes an analog engineer laugh?) | Analog Devices
I think the above user has some sort of bias towards the use of firmware based soft computing embedded systems to the point of proclaiming the use of DSP is a requirement rather than telling the truth that it is just one of the ways.