Only fairly recently has Bluetooth been available in the form of wireless TV headphone sets. Although Bluetooth is a trademarked name, the technology is leased out to many companies who use it to connect their devices. This is the same Bluetooth that lets cell phones connect to each other and to the little hands free units that clip onto the ear of people that like to walk around major department stores looking like they're talking to themselves.
In fact, I hear many people referring to those types of earpieces as "Bluetooth head sets" which, though not entirely inaccurate, does infer that Bluetooth is a type of headset as opposed to a communication format. As such, it's worth mentioning that just because it uses the Bluetooth format for communicating, this does not mean that Bluetooth wireless headphones for TV have to clip on to your ear. Again, Bluetooth is just a communication format, and does not indicate the shape or form of the headset in any way.
Bluetooth works almost exactly like RF (radio frequency). The main differences is that Bluetooth operates in calculated pulses, and that it only has a range of about 30 feet. This range limitation is both a good thing and a bad thing.
It is a good thing in that only signals within 30 feet of either the receiver or that transmitter can cause distortion. Another advantage is that other people in the home can use devices that use radio without them overriding each other. Bluetooth will generally not interfere with wireless routers or cordless phones, though there are always exceptions to that rule. When dealing with radio waves, there is always a bit of randomness to contend with, and you can never be sure exactly what's going to interact with what.
Still, it's a fairly safe bet that unless the router or cordless phone base is sitting within 30 feet of the Bluetooth transmitter, you're not likely to get any interference from your wireless headphones for TV. Bluetooth is also encoded, so although it may cause interference in the form of white noise, nothing but the receiving unit will be able to actually decipher the sounds. The limited range can also be seen as a bad thing, though, because, in some cases, people do sit more than 30 feet away from their television while watching it. In fact, with projection televisions, being more than 30 feet away is almost mandatory in order for the picture to not look grainy.
Another downside to Bluetooth wireless TV headphones is that they're still very rare, and their future is not exactly certain. In fact, a search on Amazon yielded only a handful of results, and none of them look to be made specifically for TV, which may or may not cause issues with technologies such as Dolby Surround Sound. So, although they can be used as wireless TV headphones, they might not work quite right.