I love our Snuza, it is the only thing that gives me enough piece of mind to sleep at night. Our daughter is now 9 and a half months old, and we started using this for all naps and nighttime sleep when she was about 6 weeks old. I wish we had purchased it sooner! We've only had to change the battery once in that time. The only drawback is that we occasionally get false alarms because it has fallen off her cloth diaper. I will definitely use the Snuza from birth with all my future babies. Sound/Video Clarity The Snuza Hero emits a high pitched beep when it does not detect movement for 20 seconds. The sound is certainly loud enough to be heard over a baby monitor, though I do wish that this came with a handheld parent unit that alarmed instead of alarming only on the baby. We have thankfully only ever had false alarms, from the unit slipping off her cloth diaper, and she has never woken up from the alarm. Interference Because this is a standalone unit that does not transmit sound or video to a parent unit, there is no chance of interference. Durability The directions specify to be gentle and not bend the rubber tip of the Snuza back, but we've accidentally done so a handful of times and it still works fine so I think it's pretty durable. Portability The Snuza is just a small unit that clips directly onto the baby's clothes or diaper, so it can be used absolutely anywhere. We only use it when she is sleeping at home, but you could definitely use this in the stroller or car seat as well if you wanted to.