EnOcean makes devices which harvest energy, so they need no batteries. Among them are wireless switches, which send radio messages using the energy created by pushing a switch.
These switches could be very handy for setting up a system. Stick them on any surface, and one instantly has an on/off switch available - no wires, no batteries.
Supporting EnOcean devices is a significant amount of work, as the protocol is fairly complex. However, EnOcean does a good job documenting it.