No, you’re not being paranoid. Sites really are watching your every move

True. The problem is that websites like Walgreen, which simply break with no JS, are only getting more common. I'd like to make a point of simply closing the tab in such cases, but it's not always possible.

I did this in like 2005. I don't recall it taking more than an hour. For simple sites, probably faster to just implement it than find a library and read the docs.

Collection is easy. Just capture every key even and read the location of the the mouse in a sufficiently tight loop. Timestamp everything, bunch it and send it to the server on a regular interval. You can do it in 10ish lines of JavaScript.

Playback is the hard part, depending on your infrastructure. But if your site is simple enough you don't even need a library; just load up the page the user was on and play back the data.

I'd be surprised if there isn't already a Dropbox company out there going the final 20% on this "just rsync it" comment though.