Due to the rapid development of semiconductor technology, the number of transistors of integrated circuits in unit area increases by double in roughly every two years. We then can add more circuits and functionality into a single chip. The size of electronic products certainly is reduced. Besides, because of the blooming popularity of wireless network standards in recently year, sensors have been wireless connected to provide more functionality and intelligence. They are, namely, wireless sensor network (WSN). Before long, the integrated circuit design will not only be emphasized on front-end circuits and hardware design, but also integration and functionality, which is so-called the system-on-chip (SOC) design. The first topic of this thesis is the implementation of IEEE 802.15.4 network prototype and hardware design. The main purpose of prototyping is to realize the highly portable IEEE 802.15.4 protocol stack library which can be quickly transferred to different hardwares. Thus, it shortens the time to market. In ASIC hardware design, we use WISHBONE bus as the interconnection architecture which can be easily integrated into current SOC design for an embedded system. The second topic is an application of IEEE 802.15.4 in medical monitoring, including system prototyping and ASIC hardware design, which collects the bladder pressure readings by a wireless link and ECG signals from our ASIC sensors. Finally, we realize the medical monitoring in a prototypical system.