The I-Laps system is all well and good for onroad - no denying it. But for off-road (where it may have rained?) a sensor that relies on line of sight isn't going to work great. Sure, when it's dry and dusty, it'll work fine, but any weather change (and look at the UK - it's hardly dry all the time), and the system isn't going to be effective, particularly when cars come back looking like this:
