We have the Angelcare baby monitor and I reckon it's worth every penny.

I can sleep easy knowing it will sound if he stops breathing. It's gone off a couple of times when he's been at the very ends of the cot so the monitor can't pick up his breathing - which is reassuring as we know it works! However, we've had to test it to ensure the ceiling fan doesn't 'trick' it. So keep that in mind if you use a fan in bubs room...
I totally agree.... even with the fan bit! I now leave DS's blankets off & fan off unless he really needs the fan (I turn it off on my way to bed so the room is cooler by then)

I think its definately worth the money for the peace of mind, especially if you have a tummy sleeper like me!