using this technology are able to measure blood oxygen saturation (SpO2). Some recent optical sensors can also transmit data as mentioned above. Newer devices such as cell phones or watches can be used to display and/or collect the information. Some devices can simultaneously monitor heart rate, oxygen saturation, and other parameters. These may include sensors such as accelerometers, gyroscopes, and GPS to detect speed, location and distance. In recent years, it has been common for smartwatches to include heart rate monitors, which has greatly increased popularity. Some smartwatches, smart bands and cell phones often use PPG sensors. Fitness metrics Garmin, Polar Electro, Suunto, Samsung, Google and Fitbit are vendors selling consumer heart rate products. Most companies use their own proprietary heart rate algorithms. Accuracy The newer, wrist based heart rate monitors have achieved almost identical levels of accuracy as their chest strap counterparts with independent tests showing up to 95% accuracy, but sometimes more than 30% error can persist for several minutes. Optical devices can be less accurate when used during vigorous activity, or when used underwater. Currently, heart rate variability is less available on optical devices. Apple introduced HRV data collection to the Apple Watch devices in 2018. See also Activity tracker Apple Watch E-textiles eHealth GPS watch Pedometer References External links Visualization of ECG recordings using Python program ECG-pyview A simple Python program visualizing raw data produced by chest strap based ECG sportesters. Enables to inspect ECG recordings having lengths up to days. (Open source, non-commercial use, use matplotlib.) A demo video. Biomedical engineering Diagnostic cardiology Exercise equipment Finnish inventions Medical monitoring equipment Physiological instruments