Here at INL we are developing an array of sensors which could ultimately be used in magneto-encephalography (MEG) or magneto-cardiography (MCG) applications for improving resolution and source localization, without the need of cooling. The gradiometer sensor array uses magnetic tunnel junctions that operate at room temperature with an area of about 2x2mm2 each. The first goal of this project is to create an alternative to electro-cardiography (ECG) that does not require electrical contact with the skin, and that is not influenced by the electrical conductivity of the media between the signal source and the sensor. For imaging of the heart, we need to push the limits of field detectivity of the MTJs in order to measure the weak magnetic field produced by the heart. We can then reconstruct the current sources in the heart from the measure these vector components.