Everything with a battery should have an off switch
Examples lying around in my house:<p>Bathroom scale: lovely it powers up when you tap it, but eats up 2 button cells a year for a few dozen uses a year<p>Kitchen scales, bit more use, at least once a day but again 2 button cells a year<p>electronic caliper: Same, eats up 1 button cell a year, just sitting in my toolbox<p>Strangely enough none of our kids toys with batteries seem to suffer from this problem<p>How much extra cost does a hard on/off switch add to the bill of materials?