Asus is working on a smaller version of the GTX 670, which is for mini-ITX systems that need more graphics power than what's otherwise available.
Nvidia's reference design for the GTX 670 was already quite short, but many manufacturers chose to put bigger coolers on it anyways, where a lot of the rear of the card is just plastic. Regardless, Asus has designed its own custom PCB, which is just 17 cm long. Not only this, but Asus also designed a custom DirectCU Mini cooler, which is not only shorter in length, but is also only a two slot cooler rather than a massive three slot cooler. Lastly, the card only has a single 8-pin PCIe power connector, allowing users to use just a single PCIe power cable. It's hard to imagine such a beastly amount of graphics power in such a cute little card.
Asus is still figuring out if there is a market for this card, so there is no word yet on pricing or availability.