There's a "simple solution", you can find TV SCART adapters/extensions that have RCA plugs and with a 3.5mm jack adapter you can connect to the audio input (you should have two audio cables, right and left channel, and one for video) and that way you can keep the TV signal on one of the SCART extensions and have the input audio from the headphones output on the smartphone...with the "right tools" it shouldn't be hard to set (better, only if you have a TV/Monitor already with multiple inputs/outputs).
But in these days, almost all TVs already have wi-fi (or IR, infra-red) technologies and that makes all too easy to setup, specially with a Android Smartphone that have tons of apps to connect via "direct wi-fi"...