Aching in the balls of my feet is the most common pain I get. I've tried using a soft mat which had no effect compared to a hard floor. It seems to be down to footwear - running trainers can be fine for several hours but with converse flats I'll barely last 2.
I was seeing it as gee-wit. jwit also comes to mind.
Not that I have any stake in it, but the most confusing thing to me is that it doesn't mention the words "Google Web Toolkit" until the Tutorial page. It's an abbreviation; one that describes the product quite well (a toolkit for web apps, built by Google). Silly to bury it.
I saw a video / TV program where they talked about it a few years back... possibly in the BBC series called "The Tube"(2012).
As I recall it wasn't doing actual facial recognition, but object / shape recognition, and comparing the objects in an area over time. So you'd have the outline of a person sitting on a bench and if they're still there after all destinations served by that platform (obviously depending on the line) have had at least one train, it'd be flagged up as suspicious as apparently some jumpers like to contemplate first.
Of course there must be a fair few false positives - people waiting to meet friends to either travel together or head out maybe etc, heck - I've even met someone to buy a laptop on a tube platform before... and I don't know how well it would cope if the person moved about between trains - but that didn't seem to matter much for their use case, and I'm sure they must have better tech in place by now.
Sorry I can't be more precise with a source, but I'll let you know if I find anything helpful.