seems like a computer chip in the shoes could be used to detect contact, to spot a running motion vs. walking?
Not so easy. It would need a very high accuracy of time synchronization and therefore periodic communication between the two chips, which would make it power hungry and therefore add weight that runners may not want; plus it would be near impossible to guarantee no false positives given how close walkers tend to push the boundaries. A human eye is not more accurate, just less blamable because of the implicit rule in all sports that the referee is always right.