Reddit mentions of Actiontec MyWirelessTV MWTV200KIT-01 Multi-Room Wireless HD Video Kit

http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32 I'm sure there are cheaper options too

Close, $180: http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32 They work pretty well, using one to mirror our living room tv to our kitchen at the moment.

I have Actiontec http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32/ref=pd_sxp_grid_pt_1_0 It's great for watching movies or surfing but the lag it adds just makes games unplayable for me.

Your best bet for quality and latency will be a balun or KVM device with transmitter and receiver; linked is just an example, I use Crestron and Extron stuff with great success, but it can be expensive. You will have to run ethernet cable and possibly terminate yourself.

There are wireless HDMI products out there, but I have not used them. I install AV systems; if you end up getting the wireless, will you PM me with the results?

As for the sound, with either option, HDMI carries audio along with the video. Your TV probably has an analog audio output; either a 3.5mm jack or white and red stereo RCA jacks--6 foot cables linked respectively. It will only be stereo, but it is the easiest route to take, IMO.

You haven't specified what kind of cabling or resolution you're looking for. HDMI cabling tends to be unreliable at distances of 50'-75', so I wouldn't recommend going that route. VGA will handle that distance without any problem, but you won't get full HD with VGA--you'd top out at just under 720p resolution.

I would opt for the CAT5 adapters myself if a projector is a 100% unfeasible solution. Although I do have a wireless HDMI box that works out fine for me at home I could recommend. Might not be feasible in a live setting due to interference, blocked signals and whatnot though.

This thing works well enough. I have it and am watching TV on it right now. Not cheap though...

http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32

You could get this for $180: http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32/ref=pd_sxp_grid_pt_1_0

Or this for $170: http://www.amazon.com/Nyrius-Transmitter-Streaming-Satellite-NPCS549/dp/B009E6R89C/ref=pd_sxp_grid_pt_0_1

Both of them stream in uncompressed 1080p and they claim to have zero latency. You could search other places to find them cheaper but if you're looking for 1080p, this is what you're gonna have to be looking at. You could also get a 30' HDMI cable though and route it around the edges of the wall on the ground.

EDIT: By the way, if you get an HDMI cable, don't get the more expensive ones, there is really no difference between the expensive ones and the cheap ones.

2 things Steam should do.

1. Invest into creating "HDMI + USB Wireless transmitter." I don't think that exists... but HDMI Wireless Transmitters exist... Something like that while incorporating USB devices. So I can just hit a keybind or something on my computer and send my computer to the living room. (EDIT Found something that could work. Actiontex My Wireless TV. The Steam page on Big Screen Mode, mentions WHDI devices as an option, but says they are still rough. Steam links to this page listing out different WHDI devices if anybody is interested. WHDI devices)
   
   
2. Source games like L4D2 and Portal 2 have Local-Coop hidden in their config files. To enable it you need to manually edit the config file for the 2nd controller, and type in some console commands to enable it all. Steam, needs to incorportate local coop into their PC games. If you're going to be using the living room TV, other people aren't going to want to watch when they could potentially be playing too.

You could get a HDMI splitter and connect a wireless display kit with it. Example: http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32/ref=sr_1_3?ie=UTF8&qid=1421026414&sr=8-3&keywords=wireless+HDMI+kit

There are products, but they are not cheap.

A 1080p signal, even at 30 fps is a very high bandwidth. Luckily you only have a short distance to cover, so you probably won't have issues with signal strength, but its a lot more expensive than buying an HDMI cable.

60 GHz wireless HDMI transmitter 1080p 60 Hz + audio: $175

http://www.amazon.com/gp/product/B0077LKEKQ?tag=thewire06-20&linkCode=as2&creative=374929&camp=211189

Various other tech:

http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32

http://www.amazon.com/Nyrius-Transmitter-Streaming-Satellite-NPCS549/dp/B009E6R89C/ref=pd_sxp_grid_pt_0_2

http://thewirecutter.com/reviews/the-best-wireless-hdmi-video-transmitter/

There are probably better and cheaper products than these, but I haven't researched them much so I couldn't say.

You can use something a lot cheaper, like Chromcast for example, although I believe it uses a compressed signal so it will have worse latency and image quality, and it maxes out at 720p.

These work just fine and can do a one to several broadcast.

http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32/ref=sr_1_1?ie=UTF8&qid=1410292616&sr=8-1&keywords=MWTV200R

We use them in many of our conference rooms on both projectors and TVs.

I'll just leave this here :) http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32

Yay wireless technologies :)

There serveral products which will "cast" an HDMI output from one place to another. There are both wired and wireless options.

Our household uses an Actiontec My Wireless and it works well for us. It also has an IR blaster built in so you can have a remote that lives in the spare room yet changes channels on the cable box in the other room. There is about a quarter second delay between button presses which is noticeable, but still very usable. While it has a moderate up-front cost. There is zero reoccurring costs, which is nice compared to a cable box. Whether this one will for you depends on several things.

What is the physical distance between the cable box you want duplicated and the spare bedroom?

Does the wireless have to be a problem?

http://www.amazon.com/Actiontec-Wireless-WiFi-Multi-Room-Video/dp/B005L9ZZ32

http://thewirecutter.com/reviews/the-best-wireless-hdmi-video-transmitter/