When you say “cable” are you talking about TV or Internet? In either case, this is as mainstream as it gets. You can get a multitude of wireless LAN systems with an internet gateway on the router for your computer. Most better new notebook computers even have wireless built in.
There are several readily available TV products that will take an input signal and locally broadcast it to any number of receivers within the house. You will of course, be stuck with a single cable “box” tuner unless you get one of the multiple channel models. Satellite systems come with an option for multiple tuners and wireless transmission. If you have a normal cable TV system and you would like to just split that wirelessly, I think you may have a problem.
Here is a device that will transmit an A/V channel: http://www.sweetronicsstore.com/rf-link-wavecom-sr.html
My advise is, if it’s Internet you want, visit Best Buy and look at Linksys. If it’s TV you want, get out the drill and saw (and patching plaster). It’s not that hard.