Babies sleep a lot. A LOT. Any halfway decent baby monitor needs the ability to see in the dark (IR illumination) which iDevices don't have, so unless it's relegated to monitoring play areas during the day, its usefulness is limited. That doesn't mean the software isn't well designed, the hardware is simply not fit for purpose.

I sometimes used a FaceTime call between an iPad and my phone as a make shift baby monitor. Audio only, I don’t think video is really necessary. In fact, our Angelcare monitor at home was audio only.

Ours also had sleep apnea detection (a mat to put below the mattress), perhaps the accelerometers could be used to detect lack of movement.