First of all my deepest condolences for your loss. Second, regarding infant monitoring solutions there are a ton of well funded startups and companies doing this: Kiddo and Owlet come to mind, and basically they have monitoring watches and socks, that are capable of monitoring and generate alerts for most important vital parameters: Pulse, temperature, oxygen saturation, even blood pressure.
https://owletbaby.com/https://www.kickstarter.com/projects/kiddowearable/kiddo-stay-connected-to-your-childs-wellbeingThe biggest problem is due to ENORMOUS development cost, especially regulatory certifications, these devices remain some kind of very niche, very expensive products. Another thing is as much as they try to make it easy to use and child proof, these things are in the end medical devices suitable for use by professionals, need themself constant monitoring and servicing, I have tried myself with different relatively cheap oxygen monitoring watches and devices, is extraordinarily easy to have them either not measuring anything, or giving erroneous measurements. Especially for kids that squirm and pull and bite these thing are very difficult to do properly.
So this is a very tall order IMHO, AFAIK, the holly grail of patient monitoring is the multispectral camera connected to some powerful image processing and ML extravaganza, but this makes it even more expensive and unaffordable except for large well funded hospitals.
But by all means, grief is a strong motivator, look into the topic and who knows where an idea may show up, good luck.
DC1MC