The Fozgometer is basically a voltmeter in a fancy "Audiophile" casing. If you have a good RMS voltmeter you can measure the output of both channels and achieve the same result. It will be a bit more cumbersome as you will need to connect and measure one channel at a time.
ronenash,
If one would use a voltmeter, would the voltage readings needs to be converted to decibels?