How to be sure your Canon is off

After a monumental discovery the following email to my excellent No. 1 Son who also owns one:

Oh hey No. 1, you remember how we both thought our Canon A560's ran the battery down even when off, apparently that isn't the case. When the lens is withdrawn we had assumed the camera is off but that's not always so. But then how does one know.......

Canon presently has had a battery of 34 engineers (pun unintended) working 16 hours a day since we first noticed the problem, to determine under what conditions the power is on--depending on 16,442 combinations and permutations of control settings (by actual calculation) and how the user would know.

There's a light on the front that sometimes tells you it's on but not always. It depends on the day of the week, the month (I think in September it won't come on between the 2d and 11th of the month) and how you hold your mouth when you last snapped the shutter. I have been experimenting and if they don't come up with the answer, I think I'll be able to supply it in 3 or 4 years of diligent trial-and-rerror

Meanwhile though after my monumental discovery I've experienced renewed interest in my Canon, as when the batteries are up it takes the most marvelous photos, as above; so no, please no cameras for Xmas