DD is asleep on the bed right now I develop super hearing.. and hear her when she stirs. It helps that I know she usually sits up and makes noise before she starts to crawl around.

DS was climbing off the bed safely at about 13 months, but I found he never crawled off the edge anyway, it was him sitting himself up too close to the edge that made him fall off.. took him a while to work out where to put his bum when he sat up. hehe.