I would like to find a device that:
- Plugs into the wall outlet.
- Plugs into a USB connection to a computer.
- Measures the voltage in the wall outlet.
- Reports the voltage to the computer, presumably as a HID class device. (No display needed.)
- Is powered by USB, so I can get readings when the power is failed.
- Is cheaper than buying a UPS. (Some UPSes can do everything listed so far, except that they probably provide their own power.)
- Is significantly smaller than a UPS.
- Can measure to fraction of a volt precision, and finer is better.
Just to be clear, I do NOT want to measure the voltage of the USB bus.