I remember that I wrote something with weird symbols in a margin of a history essay at one point, and somehow that got me making a phonetic alphabet (before I had even heard of the IPA, I think), which I used to annotate the pronunciation of the French words I learned. (I think I entered new words in the booklet in normal spelling starting from the beginning of the booklet, and in phonetic respelling starting from the end.)
I don't remember much about the scheme I used, save that /ʒ/ as in "measure" was written "z͆" (even though, I think, /ʃ/ as in "ship" was "š").
I wonder where I got the idea of that weird bridge above the z from. (I also think it didn't last all that long because it was a bit awkward to write.)