Wireless embedded devices are one of the fastest growing computer technologies today. Of the total amount of microprocessors sold today, 98% are used in embedded systems. Wireless embedded systems range from wireless car keys to security systems for freighter containers. Wireless embedded devices meet challenges in terms of cost, physical size, and energy consumption, which has implications for the operating systems running in the devices. This article discusses energy consumption and energy conservation, communication protocols and their implementation, programming models, and software updates and run-time reprogramming for operating systems for wireless embedded devices