Television, at least in the "bad old days" (not too long ago!) only came in wireless flavors. Cable television really gained popularity in the 1980's and 1990's. Before that, people usually just watched locally available broadcast television. This has the disadvantage that there are usually only a handful of stations available in any given location (the UHF band expanded that quite a bit over the standard VHF, but usually the UHF band in most areas only has a couple of stations in it), and reception can be hit-or-miss. With cable, people get a hundred or more channels easily, with perfect picture and sound quality. Satellite TV is also quite popular these days, and is also "wireless", although usually it involves wires going from a permanently mounted dish antenna to where your TV is in the house. The dish shouldn't be moved around with the TV because it has to point at the satellite, and a small misalignment can cause the signal to be lost.
Stereos and home theaters are also available in wireless versions, at least as far as signal reception and networking. Computer manufacturers build home theater systems which have personal computers inside. Just put a wireless network adapter on one of these, and the network connection can be free of a cable. Radio is wireless already, and putting a CD or DVD in a slot doesn't require wires anyhow, but with a wireless network, you can make your own CD's from content loaded (hopefully legally!) from the network.
But perhaps you are wondering about the electrical power. Here the news isn't so good. All the wireless gizmos I've seen are battery powered. I have seen lots of battery-powered portable TV's for sale (they are rather small and I wouldn't want to watch one for very long). Boom-boxes are battery-powered and wireless. It probably doesn't take too much engineering work to put a wireless network adapter on a boom box to give it access to the internet. Battery technology is also improving with lighter, longer-lasting batteries.
Photovoltaics are fine, esp. to charge batteries. But you need bright sunlight and quite a bit of patience to get all the energy you need. It's hard to imagine that you could build a home theater system using just photovoltaics for power -- the light the theater produces has to be easily visible above the ambient light level so the picture can be enjoyed (it's hard to watch TV in bright sunshine, and movie theaters are always very dark). A theater projecter should be brigher than its surroundings, but photovoltaics always gives you less electrical energy than the energy of the light that hits it, so there's an inherent contradiction of the requirements here. You could put the photovoltaic cells somewhere else (on the roof, say) and put the home theater inside the house, but then you'd need a wire connecting them, and then why not just plug it into the regular electricity supply?
More practical may be solar-powered portable personal audio players. But then again, using solar cells to charge batteries would be preferable because you'd want these devices also to work in the dark if need be. Many of them are rather sparing with their battery usage (I have a portable radio/cassette player which lasts about 24 hours on two alkaline "AA" batteries, and it's five or six years old already. They probably make even better ones now.).
(published on 10/22/2007)