Have one of these (similar) on order - I suspect they may not be very accurate but will compare with a DVM.
Have seen them in the past and ignored them as a gimmick.
I was gassed at work today (again) and had to sit in my car for half an hour before risking the drive home, engine running as it was only 1.5°C.
Noticed that the voltmeter rose and fell periodically. Possibly the secondary heater coming on and off.
Will be interesting to compare with the USB meter.
