To keep beating a dead zombie here, 'cause I like beating dead zombies, the best flat out method is having someone you know with you. Next is a med-alert bracelet bracelet of some kind. I use a RoadID, currently the wrist elite, its like a thick liveSTRONG bracelet with a steel med alert tag on it. (YMMV) but it is the most comfortable and noticeable I have worn and I wear it daily.