First aid kits are another item which are not a legal requirement when driving in France. This being said we personally would never leave home without having at least a small emergency first aid kit in the car.
As with fire extinguishers, in France you can be prosecuted for not assisting someone else who is in danger. If you are unfortunate to have an accident, or come across an accident where someone else is injured you will regret not having some form of first aid provision.
There are a whole variety of different first aid kits available from simple bandages and plasters to full blown packs with every type of first aid implement you could think of. Be prepared to help your family, yourself or someone else and get first aid kit in your car.