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Sparky is a toy for children who are old enough to understand the risks of fire (ages 8+). The Sparky toys come in many different forms including monsters, cars and jet planes. Each of the toys are based on the same mechanism of a piece of flint strinking a flint wheel. For the monster toy, the sparks fly out of the mouth when the child pushes the toy forward on the ground. Gears connected to the wheels spin and engage a flint wheel which creates the sparks. The body of the toy is translucent so that the child can see the inner workings of the toy (i.e. how all the gears are connected and how they drive each other). The car and plane toys are very similar in that they have wheels that turn and engage a flint wheel that strikes a piece of flint. The car would have sparks flying out of the tailpipe and the jet would have sparks flying out of the engines. The toys should have more complex gear systems than is necessary so that the children really have a grasp of how gears work together (perhaps there could be patterns on the gears so that the children can see and predict which way the gear will turn).
Construction costs should be minimal, especially considering the low cost of disposable lighters and toy cars (i.e. McDonald's toy cars). Sparky toys, like many other plastic toys, are not designed for "rigorous testing" (i.e. being smashed with a hammer). However, the toy is sturdy enough to hold together and be played with reasonably. Safety is of course the main issue in this toy. As a former owner of a very similar toy I can personally say that there has been no safety issues with this type of toy. I have run the toy over all sorts of surfaces (carpets, walls, my arm, etc) and I have never gotten burned or started a fire with the toy. I have gotten the sparks on pieces of paper, wood supports on my house, even on my skin, and I have never gotten hurt. Of course one person's experience doesn't apply to every experience, but as long as the target age group (8+) is using the toy I believe that they will be responsible enough to know how to use the Sparky toys properly.