[LorenPechtel]

That's asking for corrosion damage from the battery.

I've got a bathroom scale that goes several years on it's pair of coins even though it turns on only when stepped on. I suspect there's a physical switch involved, though.

[d0mine]

why don't they use gravity as the power source? I've seen scales that require pushing a button several times to power it. Getting rid of the button and using the full scales' surface seems like the next step.