I think Bosch is refering to connecting the voltwatch to the ignition supply pack. I think in this case, its a good setup to see if your ignition pack is still giving out the juice for the CDI.

And as for RX pack, as per Geistware, I find it very useful. Granted if I can see the volte numerically it is even better.

As for the expanded/loaded volt meter also do no good either. Most of the max loaded at 1amp. Some to 2amp. Then again in real flight situation, with all onboard digital hi torque servo, they draw easily above 2amp for 6-8 servos. So the loaded voltmeter are no better either, IMHO granted its a still a must for flight check.