Devices and systems as described herein is configured to sense a signal, such as a signal from an individual. In some embodiments, a signal is a magnetic field. In some embodiments, a source of a signal is an individual's organ, such as a heart muscle. A device or system, in some embodiments, comprises one or more sensors, such as an array of sensors configured to sense the signal. A device or system, in some embodiments, comprises a shield or portion thereof to reduce noise and enhance signal collection.