Funny that this comes up today! I was just looking into adding a keyboard monitor to my website (I have a goal of making my 'contact me' page have oddly specific information). I wouldn't show the actual keys, just show a blinking light when there's activity, but I guess the timing really could expose quite a lot of information.

I did add a trackpad monitor though. It shows my raw MacBook trackpad data.

https://varun.ch/contact/