I would love this too...a few other posts here over the years, but i can't seem to find info on ballyally.com.
RF works "ok" on new LCD TVs with that input.
I wonder if its hard to do a sort of "rgb2hdmi" like the amiga line has now, as the video output
has R-Y, B-Y, and a 2.5V "Resistor ladder" that outputs video to the modulator.