I have no problem with using a device to keep track of the arrow. But I do think it looks much smoother if you don't need to check your pockets before signaling the direction of the held ball.
One trick I heard at camp was to remember the arrow as you're counting. For example, when you have a backcourt 10-second count, instead of counting "1 one-thousand, 2 one-thousand. . .", try counting, "1 red arrow, 2 red arrow, 3 red arrow". This has actually worked great for me. I can still take a quick peek at the table to make sure I have it right if I need to. But when a held ball happens, I've beaten the arrow into my memory so I don't have to check the table or my pockets or the switch on my whistle.
As far as having an arrow at the table, I read a story (I think it had to be on this website a long time ago) about an official who used to carry a child's stuffed animal in their equipment bag. It was a toucan, with a long beak. And if there was no arrow at the table, he would leave the toucan at the table to be the arrow. There were jokes about having to "flip the bird" after every held ball.
