A sufficiently-smart spell-checker would be indistinguishable from a translation aide, sentiment analyzer, voice-recognition classifier, etc. Basically, whatever tech is required to make spell-checkers better has other uses than spell-checking, and those might be valuable.
A sufficiently-smart spell-checker would be indistinguishable from an artificial intelligence. A company producing one of those things would make billions, but not by selling a spell-checker.
I didn't mean it would be indistinguishable from all of those things (because it is an AGI and could act as any of those things if it wished), but rather that it would likely have to incorporate one or more of those things to spell better. I have a feeling sentiment analysis alone would be a pretty good next step for spelling/grammar-checking.
