Depending on your set up potentially this can be done cheaply. I'd use Xiaomi aqara motions sensors (via zigbee2mqtt), node-red with home-assistant and the LG webostv component. I can already trigger message notifications to the TV at will. Playing a video would just be about setting the input and a command to play. Presumably you could load a specific video onto a usb key and just tell the TV to play that local file (probably would work with a Nas/network file too).