Baby weight
A smart baby scale, a $8 radio, and a growth chart the whole family can see.
Why
In the first weeks, weight is the number everyone asks about. Is the baby back to birth weight? Gaining enough? As a family doc I've asked that question thousands of times .. now I'm a grandparent asking it.
The scale we bought (a Greater Goods Bluetooth baby scale) is a fine scale. But its readings live in one phone app, on one phone. Grandparents can't see them. The pediatrician can't see them. And nobody wants to type numbers into a spreadsheet at 3 am.
So we fixed that.
How
The scale. It speaks Bluetooth Low Energy. We captured the conversation between the scale and its own app, worked out the protocol (login, time sync, then weight in grams), and wrote it down.
The bridge. A thumb-sized M5Stack NanoC6 (an ESP32 board, about $8) plugs into a USB charger near the scale. It joins the home Wi-Fi, listens for the scale, and sends each weighing here over HTTPS. No phone needed.
This site. Readings land on a chart with the WHO growth curves. Add weights by hand too. Share a read-only link with family, or add people by email so they can log weights. One bridge can serve more than one baby .. or the cats.
Build your own
Everything is open source (MIT): the scale protocol, the bridge firmware, and this web app. The README has the parts list and flashing steps.
Not affiliated with Greater Goods. A hobby project, not a medical device.