Why add the expense of the tuner to the display where if it goes, so does your display to be repaired.
HDTV TV cards are just around the corner with some available now sans Mac drivers. Standard TV cards and USB devices are available to to drive TV to your screen and you can shrink the window, watch TV, and still surf rather than switch back and forth.
Or, buy a refurbished first generation 15 inch Apple Studio Display and use a VCR as a tuner to make it your second monitor/TV screen for your Mac.