Invented by a police officer, PowerFlares are LED replacements for convetional flares. They have the advantage of not emitting toxic fumes or polluting the the ground. They also tend to cause fires, such as the one seen here.
PowerFlares emit light in all directions, and can be seen for miles at night. Each unit is about the size of a hockey puck yet is strong enough to withstand being run over by trucks at highway speeds.
PowerFlares comes as rechargeable units, which are designed for daily use, and other units designed to keep in the trunk of your car or a first aid kit. Available here for $40 to $80.