I have a self-repairing* calling tree design for emergencies, if you'd like to see it.

TRO

(* most calling trees are pyramids, with each person calling the 2 or more people below him. The problem is If someone high up on the tree is busy, unavailable or can't get ahold of those below him, it could leave a large number of people unreached. The self-repairing tree solves this.)