You should think about how the military do it. Any copter over water (OK big bits of water - seas, oceans) has all crew trained and equipped with stass (which needs neither switch nor button to activate in theory). Plus I believe those fine chaps in dark blue give all their passengers PSTASS which is operated with a turn valve. A wise old QHI once said "Aviation is an expense business" and he is right. But giving people stass cannot be that expensive surely?