In this paper, we consider the problem of employing UltraWideBand (UWB) radio technology in Wireless Sensor Networks. UWB promises very high data rates (of the order of few hundred Mbps), in-built localization features and low power consumption. However, UWB radios have a high acquisition time (in the order of milliseconds). As a result, distributed Medium Access Control (MAC) solutions based on a Request/Response mechanisms suffer from increased overhead when employed in UWB based networks. To mitigate the effect of UWB acquisition time, we propose a node architecture that uses dual radios on the sensor nodes: a primary UWB-based radio for data transmission and an auxiliary narrowband RF-based radio for control information and signaling. We introduce two techniques for Medium Access based on this architecture. In the first technique, we employ the narrowband channel for the exchange of RTS/CTS (as defined in IEEE 802.11 standard) information and thus enable collision-free data transmission in the UWB space. In the second technique, we employ the concept of wake-up radios to provide signaling for data transmission. We employ a distributed channel assignment technique by which neighbors agree on a wake-up channel for each node. This channel is then used to signal the receiver of an impending transmission. Through extensive simulation studies, we demonstrate that both the techniques deliver considerable improvements in delay performance and increase the network throughput over the traditional single radio UWB solution.