One problem related to air bag light on has been reported for the 2006 Toyota Prius. The most recently reported issues are listed below.
The passenger side airbag light showed that the air bag is "off" when someone was sitting in the seat. The vehicle had never been involved in an accident where the airbag had been deployed. The Toyota dealer said it was a software glitch and repaired the problem, but he charged an $85 diagnostic fee, plus tax because the vehicle has more than 35,000 miles. I was under the impression that safety devices were not subject to warranty limitations.