Are wireless sound bars for T.V. truly wireless except for possibly electrical hookup? Is there anything that needs to be hooked to the T.V?
The "wireless" portion of wireless sound bars typically only refers to the sub-woofer and/or rear surround speakers. And then, wireless only refers to not having to run speaker-wire connections to each speaker, however, each speaker (or their common amplifier) will still require AC power for their built-in amplifiers.
The sound bar is connected to both AC power and the audio line level (or digital audio) outputs of the television. It then amplifies the front/center channels which the internal speakers of the sound bar output, and sends the sub-woofer/rear channel signal to the wireless speakers via a RF (radio frequency) signal. Some don't use rear speakers but instead create "virtual" rear speakers that appear to come from behind.
While direct wiring of rear speakers from a home theater receiver provides the best sound quality, there are situations, such as a home built on a slab foundation with a raised ceiling, where wireless rears provide an economical alternative.