If you go with the baby monitor, see if you can put it in a location (say, the other side of the wall) from where the chickens actually roost. That is, if you want to sleep at all. Take it from someone with a monitor in the coop - chickens rustle around at night more than you'd think, and when you are already spooked, every scratch of toes on the roosts becomes the scrape of a varmints claws!
If you do that, it does give you incredible peace of mind - though I find I have to turn it off when it gets really windy, too.
If you do that, it does give you incredible peace of mind - though I find I have to turn it off when it gets really windy, too.