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Yeah, I use it to see if my old remotes' batteries are dead.

They can see in IR, but they can't distinguish it from other light. Maybe that's good enough.

iPhones have IR filters over them so that doesn't work anymore unfortunately.

On my iPhone 7 at least, the rear camera seems to have an IR filter but the front one does not (or perhaps it has a filter but is less effective). So I can still test remotes in 'selfie' mode.

Doesn’t FaceID use structured IR light? If so, at least one of the cameras won’t have a filter.

The front camera usually doesn't filter IR.

They might be sensitive to IR without sufficient filtering but they're not selective to it, I think the idea here is something like a IR,R,G,B pixel format. Maybe you could get military interest in it (digital Aerochrome).

Also a good way to detect hidden surveillance cameras at night.