I have no personal experience, so take this as a lead not an endorsement; but Enocean has some neat technology(some combination of piezos and suitably designed electromagnetic generator) that allows the energy of pressing a button to be harvested into enough electricity to send a wireless signal to another device. We aren’t talking massive energy savings; but it does mean that you can put the switch more or less wherever you want without needing mains power, an AC adapter, or teeny little batteries that get replaced from time to time.
If you are feeling hackerly, you can buy modules that speak their RF protocol from digikey and friends. If not, they provide the guts for a variety of retail products(listed in the first link, ‘enocean’ might also appear on the box somewhere).
Aside from them, Insteon seems to be the big name. Proprietary; but they have a fairly robust ecosystem of compatible vendors; and, alas, the various ‘open’ home automation options are a bloody mess. You’ve got some little hobbyist knock-togethers, you’ve got some ‘ooh, IEEE 802.15.4 based; but no, doesn’t actually talk to anything except the other item in the package it was sold in…’ crap, an abortive alphabet soup of ‘G.hn’ stuff, various Wifi-based things that are brutally overpowered(and power hungry) for the purpose of low-speed signalling; but which use Wifi anyway because all the purpose built RF standards are proprietary, insane, or both. Not pretty at all.