Peace of mind, some say.
I've been hearing and reading a lot about new mothers who monitor their babies all night. At the slightest beep they're up and running to check out what's wrong.
Personally, I wouldn't be able to live like that. We were given a monitor at our baby shower and haven't used it. I figure, if something truly dramatic were going on I'd hear it down the hall.
The morbid thing I have to wonder is, what would the average parent do if they found their lifeless baby in the crib? -A scary image, I know. I remember one time my son was in such a deep sleep that he didn't move a muscle when I caressed his face during a nap. I poked his belly and I still got nothing. Finally I yelled his name and whisked him into my arms, only to have him stare back at me like I was crazy. I was all ready to jump into my basic resuscitation skills, though it felt extremely different when the 'patient' is your own child.
I highly recommend that parents and caregivers be comfortable with basic CPR. All the nursery gadgets in the world would be useless without it. I know a lot of hospitals offer community courses for certification. If you don't have time for that, check out these links (I have to say that the YouTube stuff isn't official, but it's better than nothing):
Of course I hope and pray you'll never have to use this information.