The low quality of wireless links leads to perpetual packet losses. While an acknowledgment mechanism is generally used to cope with these losses, multiple retransmissions nevertheless occur. Opportunistic routing limits these retransmissions by taking advantage of the broadcast nature of the wireless channel: sending packets to multiple receivers at once, and only then, based on the outcome, choosing the actual next hop. In this paper, we first study the potentials of opportunistic routing in energy-constrained wireless sensor networks. In particular, the reduction of retransmissions due to the broadcast advantage is balanced with the arising need for coordination to avoid duplicate packets. We then propose Coordinated Anypath Routing, an opportunistic routing protocol designed for wireless sensor networks, in which the coordination between receivers is handled by an overhearing-based acknowledgment scheme. Our protocol may be used to minimize either retransmissions or power consumption, and our simulation results show that, with lossy links, energy savings go up to 7%, even for small networks of 20 nodes.