Using your TV as a giant tablet is probably a bad idea, considering you won’t be able to reach the screen all the way from the comfort of your living room couch. If you’d like to use a TV as an alternative to a giant touchscreen computer like the Microsoft Surface Hub, though, the Touchjet Wave should do the trick.
When clipped on top of the TV, the device immediately turns your living room display into a functional Android tablet. Not only can it run any compatible app from the ecosystem, it can recognize taps and gestures, too, allowing you to enjoy a large computer experience, sans the costly investment one would entail.
Touchjet Wave uses infrared technology to recognize finger movement in relation to the TV screen, sending all its readings to the onboard processing unit, which then translates it into gestures and taps that Android can recognize. It can mount onto any TV between 20 and 80 inches in size, provided it has an available HDMI slot. Housed inside the unit is a 2.0 GHZ quad-core ARM Cortex A9 CPU, 1 GB of DDR3 RAM, and 8GB of flash storage, so it’s not exactly a high-end Android machine, but it does have both WiFi and Bluetooth connectivity, as well as two USB host ports for attaching peripherals (e.g. an external hard drive), so it should be serviceable for a whole load of productivity and entertainment applications.  It comes with an infrared stylus.
Want to use it while lounging on the couch? Not a problem, since the whole thing can be controlled from the accompanying mobile app (iOS and Android). Do note, it will need to be plugged to a wall outlet the whole time, so you’ll end up with another cord to add to the mess of cables in your media cabinet.
An Indiegogo campaign is currently running for the Touchjet Wave. Pledges to reserve a unit starts at $119.