Would this also work with curries?

Hmm... the 'Ring-Sting-O-Meter'

It's easy to know how hot a chilli-containing dish is though - it depends on what kind of chillis you use, and how many of them per portion, and if the seeds are left in or not.

I mean, it's well known what types of chillis are the hottest, and what strains are milder, and so forth.

Dude, the morning after a really hot chilli, it's not my /head/ that ASSplodes...

Way back in the 1970s I worked with an optical analyzer that was capable of measuring the capsaicins in chilis.

Near Infra-Red Reflectance Spectrophotometry can measure the capsaicins by bouncing light off the samples and get the answers back in 15-30 seconds. It was good enough that Schilling bought a few machines to use in their spice buying and blending areas.