Using ordinary LEDs and photodiodes to measure oxygen saturation is not what I would consider "grand theft."
U.S. Patent No. 10,912,502
28. A user-worn device configured to non-invasively measure an oxygen saturation of a user, the user-worn device comprising: a first set of light emitting diodes (LEDs), the first set of LEDs comprising at least an LED configured to emit light at a first wavelength and an LED configured to emit light at a second wavelength; a second set of LEDs spaced apart from the first set of LEDs, the second set of LEDs comprising at least an LED configured to emit light at the first wavelength and an LED configured to emit light at the second wavelength; four photodiodes arranged in a quadrant configuration on an interior surface of the user-worn device and configured to receive light after at least a portion of the light has been attenuated by tissue of the user; a thermistor configured to provide a temperature signal; a protrusion arranged above the interior surface, the protrusion comprising: a convex surface; a plurality of openings in the convex surface, extending through the protrusion, and aligned with the four photodiodes, each opening defined by an opaque surface configured to reduce light piping; and a plurality of transmissive windows, each of the transmissive windows extending across a different one of the openings; at least one opaque wall extending between the interior surface and the protrusion, wherein at least the interior surface, the opaque wall and the protrusion form cavities, wherein the photodiodes are arranged on the interior surface within the cavities; one or more processors configured to receive one or more signals from at least one of the photodiodes and calculate an oxygen saturation measurement of the user, the one or more processors further configured to receive the temperature signal; a network interface configured to wirelessly communicate the oxygen saturation measurement to at least one of a mobile phone or an electronic network; a user interface comprising a touch-screen display, wherein the user interface is configured to display indicia responsive to the oxygen saturation measurement of the user; a storage device configured to at least temporarily store at least the measurement; and a strap configured to position the user-worn device on the user.