Getting your lap times is very easy with the Hot Lap Systems made by Longacre Racing. These systems consist of 3 pieces: the display unit, receiver and infra red transmitter. The display unit will display your lap times and keep timing your laps after crossing the infra red beam from the transmitter that is placed at trackside. You can review your lap times off of the display unit after all of your laps are completed. This can be used as a great learning tool!
Other alternatives are simple stopwatches or the GPS guided Traqmate System. Traqmate is a vehicle data acquisition device that uses a high-speed GPS receiver and high resolution accelerometers to track and record the speed of a vehicle, its absolute location, and forces acting on the vehicle. Use Traqmate's unique modes such as lapping, drag racing, autocross, braking, g-force, and GPS compass to have fun, tune your car, or even find your way to the track!