I thought about having a small flag on a really sharp antenna-style post sticking on the left side of the bike. About a foot or two, laying parallel to the ground should do. That would encourage drivers to give a bit more room, as they are probably more afraid of getting their car scratched up then they are of hitting someone.
That still does nothing about the distracted driver. They aren't going to see the flag if they're looking down at their phone laughing and writing a text.
