We have an Angelcare Monitor and it is great. It has a breathing sensor under the matress and it alarms when there has been no movement or breathing after 20 secs. We have used it constantly since Amy was born. It is more expensive than the sound monitors but it is worth it for piece of mind. As DH says 'What does a baby sound like when it stops breathing' referring to the sound only monitors as they wouldn't pick it up (unless you were listening for every sound).