Assuming the spectators are a safe distance from the track. . .
what's a convenient height for the distance sensor, that works with one or two candidate sensors in the hyperlink?
The sensor example graph had the same voltage output for two different distances, so we need to have the sensor working in the graph area to the right of the peak.
Decide
the longest vertical distance from the road to the sensor mount that is "normal" and
the shortest vertical distance from the road to the sensor mount that means a wheelie is in progress.
If there is overlap here, that may be a problem.
Then the task is to find or design a field-adjustable comparator circuit to output the limiting signal to the engine control, that mates with the sensor output and the engine control input.
This circuit may need a metal box to shield it from radiated ignition noise.
Including the box and shipping costs, the total mat'ls cost may come to $15.
Then testing.
Sometimes, what is built works exactly as designed, but once it's built and operating, it becomes clear that something else is needed.
I guess we cross that bridge when we come to it.