Confusing headline, I know, because this is going to take some explaining. This is the SLG 3000, and it apparently can make old games played on a new TV look as good as they were originally designed.
How does it do this? The SLG 3000 is a circuit board that you plug your console into, and then attach the board to the TV. It's then able to create artificial "scanlines" on a fancy HDTV, something most of these displays are naturally programmed to soften or bleed out.
What this means in practical terms is that your old games that were made using pixels will now look more pixelriffic, as each individual pixel will now - in theory (I haven't seen this in the flesh) - be displayed with more clarity, along with that "lined" effect you could only get from old CRT sets.
You can get them for $70 from the site below.