Built in Memory: With a 40 hours built-in memory, EMAY Sleep Oxygen Monitor allows you to store overnight and continuous blood oxygen saturaiton levels & heart rate during sleep or other ocassions. Record First, Sync Later: Does not require real-time connection to smartphone. Wear it to record, take it off to sync later whenever you want. Free iOS/Android App: 1. Review historical & granular data second by second; 2. Sleep report with detailed analysis & trends of your overnight blood oxygen and heart rate; 3. Export CSV file of data list for further analysis or sharing. Accurate & Reliable: Accurately display the readings on a large & rotating digital LCD screen, and store your data second by second without interval simultaneously. We're here for you: Our California based team is happy to assist you with whatever questions and support you may need within 24 hours. Intended for sport and aviation use only, not for medical use.