Yeah, they've had them for GBAs and GBCs now too. I think they're neat, lots of people do the IPS screen mods on their old Game Boys these days, and now for a few bucks more you can get some extra wires to solder and a link cable to optionally do TV-out. Not a necessity by any means, but a pretty cool novelty in my book.
And to esmith13, yes link cables can still properly work, so long as you remove the resistor on the EM3 of the GBA. This is for the GBA anyway, not sure if the regular Game Boy has a similar resistor to remove. However, the wireless GBA link adapter no longer works with this mod, not a big deal as it was an optional way to link for only a small handful of games.