RE: "Tower Pro" "Volt Watch"
I think the Volt Watch is a handy item, it gives a quick visual. However, I'd take the time to cycle the battery down to the caution level where the yellow light comes on and read the voltage. I checked a battery this last Sunday that had just gone into the caution range on a friend's airplane it read 4.6 volts which is below a level that I'll fly at.
Personally I don't like to fly much below 5 volts so I use 1100 milliamp batteries in my airplanes which gives a lot more flying time. IMO it doesn't take much time to check the battery with a meter between flights. Old School I guess?