Each participant in the HMDN will have a bumper sticker or a decal with their ID number. Simply key in the ID number of that vehicle and send him a friendly reminder of his poor driving practices. Likewise if they perform an act of courtesy like allowing you to merge into traffic, you can send a kind "thank you" to that vehicle. So when you accidentally get distracted at a green light and you hold up the traffic, rather than getting a series of dirty looks and obsene gesture waves, you can now get your complaints through your HMDN unit.