Most connected light switch products require hardwired installation. Take the Belkin WeMo Light Switch. It has a simple enough setup, but you still have to replace your current light switch with Belkin's smart version.
Palo Alto, Calif. startup, Switchmate, has just launched a product of the same name on Indiegogo. Not only is it supposed to do the same thing as the Belkin WeMo Switch for less money (you can get one for $39, two for $69 or three for $99; Switchmate isn't currently available internationally), but it also claims to have a ridiculously easy installation.