Angelcare Digital Sound and Movement Monitor
I love this! It's only went off once and that was because my son just stopped breathing for some odd reason.
As a first time mum, I was constantly worried about SIDS. Since getting this I was more comfortable sleeping in and not worrying 24/7 checking if bub is breathing.
Neg - frequency can go crazy at odd moments. I still can't figure out what causes it.. overall its only happened a few times. Still worth getting :)
Price - quite expensive