In card games it’s useful to remember what’s been played, either one is playing blackjack or just a fun competitive game with friends.
But for many people learning memorization techniques from scratch would be a tough sell. So an easy way to introduce memory techniques could be to sell a deck of cards with actual pictures of a PAO printed on the cards.
So one would get someone from Fiverr to make drawings of the playing card mnemonics here:
And then buy custom decks of cards online for cheap, with the drawings. And sell them off Etsy at a premium. It’d be a nice birthday or Christmas present to introduce someone to memorization techniques, and one could print “By the Art of Memory” on the cards. I’d buy a deck if it was available.
I wrote “or just earn cash” in the title, but the most important thing IMO would be to spread the Gospel of memorization techniques – regardless of whether one uses it to promote software or not.