Emerging technologies like ZigBee or Ultra Wide Band (UWB) Radio, based on the new standards of the IEEE 802.15 family, will, in a near future, compete with and/or complement Bluetooth technology in the development of Wireless Personal Area Networks (WPAN’s), capable to satisfy the increasing demand of high bit rate data transfer links as well as low power and small size constrains. Nowadays coexistence and interconnectivity of Wireless Local Area Networks (WLAN’s), WPAN’s and mobile phones is just the first step towards the implementation of the so called Ambient Intelligence. The main characteristics of this new paradigm are: ubiquity, transparency, and intelligence. In this context, sensor networks are the first front of the communication chain. Thus, most of the wireless data transfers will take place at very short distances and most of the information flow will be performed at very low rates. To implement the RF transceiver devices constituting sensor networks in an Ambient Intelligence environment, several challenges still need to be solved, among them: packaging (SoP vs. SoC approaches), powering (low power, batteryless systems, energy scavenging) and system architecture (new simplified direct conversion approaches). All these matters will be considered in this work.