Is there a cut-off switch for the passenger air-bag?
No, just as in Honda’s other two-seater, the S2000, there is no provision for disabling the airbag when carrying a small passenger. The Insight Owner’s Manual has a large section on child safety that tells you to move the seat as far back as possible when carrying a child. The Insight includes a loop at the rear of the cargo area to attach a long strap from the top of a child seat, over the top of the passenger-seat headrest, and extending to the back of the car.