For the slip resistant material, I don't know if it exists, but something that isn't a dust magnet would be great. I've noticed with my SpaceNavigator that the ring of rubber on the bottom tends to accumulate dust and start slipping until I wipe it down periodically. Again a bigger deal for them, since their 6-axis devices include pushing sideways as an input.
As far as software support, Mischief does 1px increments with [], so that one's easy. And open source programs like GIMP and Blender could always be modified if needed. So I guess I'm not too worried about software.
This is a kind of niche thought, but I wonder if I could suction cup it to the back of a Surface Pro. I tend to sketch with the tablet in my lap and no good place to set a Flow. Chairs with no tables, flopped on couches, etc.
Went ahead and backed it! The $20 worldwide shipping is a bummer, but I'm glad it's been priced into it. IIRC that's one of the big problems that Apollo Pens ran into.