Smart switches, like the one from Elgato's Eve line, are wireless in - wall switches that are installed in place of regular light switches. (imore.com)
The Eve Light Switch (USA & Canada only) is the world's first light switch with HomeKit technology built in allowing you to do much more than just any old regular light switch. (pocket-lint.com)
Unlike regular light switches though, there's no drilling into walls to connect to your mains power supply, instead it's powered via a battery. (t3.com)