The devices with sensors and actuators have to be linked, which isn’t always cheap using wires; many of these systems have to communicate wireless. The devices should stay cost-efficient, particulary with regard to their own energy consumption, which often have to be covered by (primary) batterys.
In research an own term for these linked systems has been established: the area of ‘sensor networks’.
However, sensor network research was often motivated by a military context in the past; the results could not be transfered easily to civil application (or even to actual working systems). In addition sensor networks were cultivated as a completely separated technology sector, instead of integrating them into bigger networks like the Internet.
With the standardization of IEEE 802.15.4 and 6LoWPAN there exist standards for wireless connections between cost-efficient, energy saving nodes in the meantime, a first step towards the Internet of Things, which deserves its name. However, it is less clear, which application architectures should be used above these base standards to allow global wide-spread applications in the smart energy/home automation sector: As the Internet existed for decades, before the application “web” initialized its breakthrough, sensor networks are also waiting for the decisive impuls.