I'm not recommending these nor am I going to order them. I just thought I'd share a funny alternative to a money belt: socks! You'd have to have big calves for these to hold your passport. No shorts or leggings either.
There was a similar product on Shark Tank for cell phones. You would need a whole set of them or else sink wash them every night.
And even in the photo it looks like the passport will get slightly bent - not good now that they often scan the passport and don't just look at it. I don't think there would be a lot of demand for this.
A new way to look like a tourist! Oh, not for dresses & capris? LOL!
On the serious side, besides the physical size limitations, it would be an easy way to accidentally drop or slide out unaware something vital onto the ground.
I put some emergency cash (larger denomination and sealed in tiny plastic bag) under my shoe insoles.
Mindfulness, sounds like what I used to do on the streets and subways of New York City!