Abstract A closed-loop system for autonomous management of disease symptoms can provide better care for patients who have chronic illnesses, and improve the healthcare system with personalized medicine and lower costs. Wireless electronics play a key role in forming a closed-loop network between body and computer. Computers can continuously utilize detected physiological signals from body, analyze conditions by adaptive algorithms, and directly deliver therapeutic stimulation to the tissues. Two examples are introduced in this chapter, including neural and gastric electrical stimulation applications targeting management of neurological and gastric disorders. System designs and experimental results illustrate the feasibility of the feedback-based stimulation to alleviate symptoms. Wireless signal transduction and wireless power transfer mechanisms across tissues make it possible to eliminate battery in the implants for long-term use and reduce implant size for endoscopic implementation. Practical considerations for efficient wireless power transfer with small antennas are discussed.