Compact portable wireless devices and antennas for compact portable wireless devices are provided. The compact portable wireless device may be part of a piece of sports equipment. A compact portable wireless device may include a transceiver module that is used in communicating with equipment such as a handheld electronic device. An antenna for a compact portable wireless device can have a relatively small size while exhibiting high efficiency. A planar ground structure for the antenna may be formed from a circuit board on which integrated circuits have been mounted. A curved inverted-F resonating element may be attached to the ground structure. A battery may be provided to power the compact portable wireless device. The battery may be used as a parasitic antenna element.