Detect Decaf with D+Caf
These tiny strips can be dunked by the paranoid into a steaming cup of joe to determine whether it is truly decaf... or, I suppose, by the bulging-eyed caffeine addict to guarantee they haven't been accidentally slipped some Sanka by mistake.
How to detect the Decaf scamsters [Medgadget via How to detect the Decaf scamsters [Medgadget via Slippery Brick]

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Being a vegetarian, I've always wanted something like this for detecting meaty presence in my food/soup.
Too bad it looks like it's a yes/no device, not an analog device that can tell me how much caffeine is in my pick-me-up go-juice cup of joe.
actually... decaf has no bite, it always seems to me as if there is something very substantial missing from it.
or maybe i'm just addicted to the stuff
Don't make me De-Caf, you wouldn't like me when I'm De-Caffeinated.
The big issue I see with these is that even decaf has some caffeine, sometimes quite a bit.
The smaller issue is that when I was a server and intentionally served the wrong coffee it was always serving decaf as regular, and nearly always when we were already closed or when the customer was being a complete jerk.