A wearable device includes a housing, a rechargeable battery disposed within the housing and a short range transceiver for near field communication disposed within the housing. The short range transceiver for near field communications comprises a core and a plurality of coil turns wrapped around the core to thereby form a coil. A charging circuit may electrically connected between the coil and the rechargeable battery and configured to charge the rechargeable battery using electromagnetic waves received by the coil.