Mesh networks are fast becoming a standard topology for RF enabled devices. They allow a large number of low cost and low power nodes to aggregate and disseminate control and data information while only requiring a limited number of more expensive and power hungry gateways that connect to the core network.
This allows the network to support large physical areas in a robust and easily scalable manner by routing data between themselves, rather than all of them connecting directly to a central server.
Mesh networks are ideally suited for applications where a large number of sensors or control elements are needed and hardwiring them would be prohibitively expensive.