It's called Calligrapher. I have a Samsung Note 10 which comes with a stylus so it's definitely easier to write on the phone. It's from the Play store so not sure if iPhone users can download it. https://play.google.com/store/apps/details?id=com.mark.calligraphy
I’m assuming you mean like this? https://www.amazon.co.uk/Acrylic-Crafts-crafts-Non-colors-Rich-Pigments/dp/B01EVJ8Q0G/ref=mp_s_a_1_2_sspa?adgrpid=53660813752&dchild=1&gclid=Cj0KCQiA0fr_BRDaARIsAABw4Evs0h3UbCFcMTOZeX55HWPed9-Aq53f-F9UArTr4k_7SA3PwPLN-u0aAvhcEALw_wcB&h... and how long do they last?
I'd probably not use markers on concrete. You'll kill the nib. Switch to solidified paint markers (Amazon Link)
I don't quite jive with the A U connection. If you're set on a oneliner, maybe connect the foot of the right of the A to the A crossbar and make the right side of the crossbar, rather than the left, connect to the U. Might make the tag look a little cleaner and might save you some time, too.
Pretty cool, though, keep working on it.