All you in rope access seem to have the coolest devices.
What specialized device would be good for toprope solo? Something which slides uprope with minimal resistance, catches falls reliably, and can be used as a descender.
Just stick with an eye-n-eye, a pulley, and depending on your set up possibly a rope wrench. It's simple and reliable. Things like the rope runner, zig zag, etc work great but are too finicky. Also I don't know how well they would hold a climbing fall since most arborist falls are more of a swing. A good friend of mine went all in on the rope runners and other gadgets, but is starting to scale back after burning the crap out of his hands after his roperunner failed to fully engage because something minor (like part of a leaf, I can't remember exactly what it was) kept the tiny spring from working correctly.....
The rope runner is absolutely awesome for tree work but I wouldn’t use it for rock climbing. It would feed and catch like a dream come true, but it would just be too finicky with catching falls against rock because of how you press the top beak down to disengage friction from the rope. Same with the zigzag, and basically any of our stuff.
Nothing an arborist uses regularly would be ideal. Arborists should never have significant falls onto their gear. The only dynamic movement would be from swinging to other branches. The tazlov is good for soloing, but arborists don’t actually use those on a regular basis. I actually only know of one tree guy that even owns one.
The art lock jack 3 might be good, but again, falling could have weird things happen if you smack the lever.