Mechanical Keyboards

An eye tracker would be interesting, but the tech would also get badly misused.

It already is. The main purveyor of eye tracking tech markets it mainly for use in ways that are barely ethical, although they are careful to couch it as "research."

But, being able to abuse a tool doesn't make the tool bad. I still want a good one that doesn't require me too wear special equipment, but gives pixel-level accuracy.