Is there a font that would be easy for me to read with practice (and maybe offer some benefits over Latin characters) but would be illegible to normal people reading over my shoulder?
Google turned up a lot of discussions of writing systems for conlangs, but nothing that’s actually usable.
I prefer the pigpen cipher. It’s quick to learn and I’ve never met another person who saw it and knew what it was. I used it on notes that I passed to my girlfriend in class because teachers couldn’t read it.