When I had my kid I did a lot of research into the least invasive ways of tracking their sleep and found the data usage/permissions of so many apps alarming.
I ended up settling on this fantastic app simply called Baby Tracker. This app had clean UI, was customizable, synced all data directly with iCloud to avoid third party storage, and could be shared across multiple iCloud users so my partner and I could track everything easily. I’d highly recommended it.
One of the other perks with iCloud sync is that I can pull the data myself so I could fetch the raw sqlite DB rather than rely entirely off the export feature. I did that a couple times for some fun stuff like checking how many diapers I’ve used (a lot) but there wasn’t any easy off-the-shelf way of mapping the sleep data so I wrote something up using D3.js. Results: