If there are other cars in the race that you know will actually start, you can use InSim's IS_CSC packet, which is sent when a car starts moving; you could then have your app send the command to shift up with either /press or using the IS_SCH packet to send the key corresponding to shift up (but you should check they are in neutral before doing that, which you can do using OutGauge or OutSim).
This assumes your customers are actually pressing the right pedal at least, even if they forget to shift up
with this at least, they would start moving shortly after any car does - which means someone who jump starts will cause everyone else to do so as well, if they're not holding the clutch.
This assumes your customers are actually pressing the right pedal at least, even if they forget to shift up
