I have a breathing monitor (different to the motion/movement ones) I only got it for the second child because I didnt know they were available when I had Luke. I love it. It definately works. Every time I pick him up and forget to turn it off it goes off. It has never been off yet by misatake or for real which I hope it never does. It was pretty expensive but I'm surprised how much better I feel having it.

I also do what everyone else has said. Except I don't co-sleep (well only when I fall asleep feeding through the night)