We used an Angel Care monitor with DS. There is no evidence that it reduces the risk of SIDS, but it sure helped me to sleep better. We moved him to his own room around 2-3 weeks because I realized we were keeping each other awake, and it was so nice to wake up and glance at the monitor to see he was still breathing....I know, a little crazy.
We did have one time when the alarm went off, and when we got to his room, his was sort of coughing, so it did make me think he might have stopped breathing for a few seconds.
We didn't have any false alarms with ours, but there were a few nights when we took him out of the crib to nurse and forgot to turn the alarm off....and scared the pants off of whoever was still sleeping.