What features actually matter when buying a pulse oximeter?

For most home users the core signals are a clear SpO2 and pulse-rate readout, fast reading time, and reliable auto-on/auto-off. Higher-priced units add a perfusion index, plethysmograph waveform, adjustable alarms and Bluetooth app logging. Across the verified-purchase reviews we read, display readability (OLED) and consistent fit were cited far more often than advanced features.