We report noise measurements on Au–InAs hybrid structures involving a high-mobility two-dimensional electron system. Such structures show the extraordinary magnetoresistance (EMR) effect. We find excellent noise performance at room temperature close to the Johnson noise, which is in particular important for a technical application. At 4.2 K and in a magnetic field of about 1 T the nonoptimized EMR device is found to exhibit a low magnetic flux noise, offering the perspective of sensor applications also in a high magnetic field and at cryogenic temperature.