This paper presents an energy harvesting electromagnetic MEMS sensor that can detect the frequency of environmental vibrations. The device is composed of a number of serially connected coils that are fabricated on parylene cantilevers in different lengths, and can output the frequency content of ambient vibrations while harvesting electrical energy in a wide band of predetermined frequency range (3.7-4.7 kHz). The sensor generates an output voltage at the ambient vibration frequency by virtue of the relative motion of the cantilevers with respect to a magnet through electromagnetic induction. The induced voltage is processed by readout electronics to extract the frequency information. The sensor also scavenges energy that can be used to increase the life-time of the power supply of the readout electronics.