Our patent-pending MEMS magnetic sensors work by detecting extremely weak forces on permanent magnetic particles. We have developed a suite of sensors that measure different magnetic signatures for various applications. Of the key advantages of our approach is that we directly measure the spatial gradient of a magnetic field. Since fields die off quickly as you are spaced farther from a source, this approach enables enhanced immunity from interference of other sources as well as selectivity of the source you are close to. Moreover, we achieve very high sensitivity (<1nT) in a small (mm-scale) packaged sensor.