This paper gives an overview of several energy-efficient short-range transceivers implemented for IoT and smartphone-based WPAN systems. For high data rate applications, an ultra-wideband (UWB) proximity transceiver for a smartphone-based sharing desktop platform with secure screen-mirrored display is presented. As to low data rate applications, wideband and narrowband transceivers based on proprietary modulation schemes such as very-wideband (VWB) and frequency-domain OOK (F-OOK) are introduced by considering energy efficiency, bandwidth efficiency, and communication distance.