Electronic and photonic microsystems realized in the form of integrated circuits (IC) has been revolutionizing numerous fields that traditionally exploit bulky implementations. The advantages stemming from device miniaturization have opened up wide and growing opportunities to design for unprecedented functionality and enhanced performance. Leveraging novel CMOS and silicon photonic IC designs, this thesis presents four energy-efficient systems focusing on sensing and communication techniques: first, a somatosensory feedback system, composed of wireless body channel transceivers and implantable sensor nodes, is proposed to restore a sense of touch to a paralyzed hand; second, an analog SoC is implemented for neural signal recording and processing, achieving accurate and unsupervised classification of action potentials; third, a monolithically integrated, power and area efficient PAM4 optical receiver is developed for a wavelength-division multiplexing (WDM) system achieving 1 Tb/s aggregate data-rate; finally, an electronic-photonic lab-on-chip with optical power and data transmission is proposed to utilize the long-reach and low-cost fiber interconnects.