I've got a first aid kid in my pack when I commute, and I've stopped to help others out. But I don't have one on the road bike, where I probably need it most. I've thought about it, but I'm already carrying so much junk, and I can't really imagine what would be most helpful and what would be not helpful at all. There are a few places we ride that are out of cell range, where there aren't many passers by, that would be very bad places to have a medical emergency and no first aid equipment.

I do always have extra food and water, because the most likely medical emergency we would experience would be heat exhaustion/stroke. But I really should think about a first aid kit for my seat pack. It would need to be small. If I have a first aid kit in my car, house, and backpack, I should certainly have one on the bike.