This paper focuses on routing over multi-hop and multi-technology wireless networks, referred to here as heterogeneous routing. We consider a set of mobile users interested in communicating with several access points (APs). Multi-hop routing, possibly across different transmission technologies, is exploited to extend the coverage for those users that are not within the transmission range of any of the APs. This is implemented through the Ambient Networks (AN) architecture, by means of its functional entities (FE) and in particular exploiting the Composition FE. In this architecture, FEs are used to estimate the system conditions across technologies and possibly networks, by operating in a cross-layer fashion and interacting with each other and with standard protocols. Our evaluation of AN heterogeneous routing is carried out via ns2 simulation, through a careful modeling of the considered radio interfaces. At the end of the paper simulation results are discussed to prove the effectiveness of the AN architecture in the considered scenario.