A new optical sensor developed by the American National Institute of Standards and Technology was successfully tested by the Physikalisch-Technische Bundesanstalt (Germany) in the "magnetically best shielded room on Earth." The sensor does not need advanced cooling and is very small. Its suitability was proven for biomagnetic measurements in the picotesla range. So, magnetocardiographic measurement devices -- to be used as a supplement or an alternative to the ECG -- could become simpler and less expensive.