Vitality AI Coach turns your Garmin watch data into plain-language coaching. Ask in any language: why is my Body Battery low, should I train today, how does my HRV compare to my 30-day baseline? It cross-references HRV, sleep, stress and training load to reveal the patterns behind the numbers. 100% self-hosted — run it with Docker in under 5 minutes, data stays on your machine. Works with Groq, OpenRouter, OpenAI, Mistral, Google AI or offline Ollama. Free, open source (MIT).