I enjoy cycling, karting and I'm JUST getting into slot car racing with computerized timing system. At the moment I have a Micro Scalextric with a reed switch hot glued beneath the circuit, this is hooked up to the parallel port on my laptop and every time a car runs over the reed switch, it counts the lap. I need another one for other lane at mo but it works. Soon I'll be getting a Ninco 1:32 scale set and using photodiodes lit with leds for timing, you put the photodiodes beaneath the circuit, looking through a hole you drill in the circuit then have the led light shining on them. When the beam of light is broken by a car passing over a photodiode, it counts a lap. Simple but I love it lol.