This paper presents a power aware routing algorithm for WSN exploiting application features and the radio frequency map of the deployed sensors. The suggested methodology can be applied to applications requiring data acquisition from semi-static medium-size networks. The improvement over traditional routing solutions derives from the fact that routing paths and optimal transmission powers are identified through an accurate simulation of the target application (not only at the routing layer) which uses real information such as the power response of the links. The methodology, tested on MICA2 Wireless Sensor Networks, provided a reduction of power consumption of about 40% over the "MultiHopRoute" routing algorithm considered in the TinyOS community.