My Oura ring knows how I slept, but it can't see my bedroom. So I built a small box with an ESP32 and four sensors (CO2, temperature and humidity, noise, and a magnet switch on the window) that writes the room down every two minutes. A Google Apps Script lines every 5-minute point from the ring (heart rate, HRV, sleep stage) up with the room readings from the same minutes, and every morning I get one report in Telegram. Code does all the maths. NVIDIA Nemotron, running on Nebius Token Factory, only turns the facts into a message a person wants to read, and code checks every field before it is sent. What seven nights showed: on my hottest night (23.1 °C) my HRV was 32 ms against 42 on my other nights, and my pulse was 69 against 60. Seven nights is a hint, not proof.