For me, good boots, good leather with armor at least in the sholders and elbows and a good helmet, decent size rear mirrors and of course good riding habits. When i ride i am a mr bobblehead, i always know whats behind me and beside me and of course where i am heading, if practiced it becomes second nature, also experieince will tell you when a cager is about or can cut you off or cause grief, it will be come instictive after a bit. Don't think i would ever consider an air bag or anything like that.
