I was excited when I discovered the Batt-O-Meter because I had this idea myself about 10 years ago. I worked with 2 electronic designers over a 12 month period, but we could not solve the riddle of how to compensate for differences in circuit "load" that the meter would read at the jack. The Batt-O-Meter has a microproccessor which analyzes the load of the circuit to produce the correct battery reading. I have tested the accuracy of the Batt-O-Meter and find it to be excellent.
I highly recommend this great product.
Requires a 9V battery, not included.
Please click below for a video demonstration.