Wireless speakers are becoming increasingly popular. In general, these are based on Bluetooth, RF (Radio frequency), WiFi or audio vision frequency technology.
It is powered either by batteries or by an AC electric outlet.
RF speakers have the potential for RF interference with other signal sources like cordless phones. The technology is readily available and is easy to implement.
Wireless Bluetooth speakers work with nearly all Bluetooth enable devices. Audio fidelity is often a step down from the non-Bluetooth options like AirPlay speakers — but a lot of people can’t hear the difference, and the quality of Bluetooth speakers has improved in recent years. Note that many Bluetooth speakers are designed with rechargeable batteries, so they can be moved from room to room with ease.
Speakers that uses other wireless signals like Airplay speakers or Wifi speakers generally have better quality but is limited by the higher power consumption and therefore the need for a constant power supply. The technology is also slightly more expensive at this point compared to Bluetooth and RF.
So the above is a quick summary of wireless speakers.