Apple was the first hardware manufacturer to bring out computers featuring the new Thunderbolt data port with its newest MacBook Pro refresh approximately three weeks ago, but the underlying technology was developed by Intel - so pretty much any computer manufacturer has access to it. The new protocol uses the rapidly popularizing DisplayPort connector (think an even newer version of HDMI) but it can transfer data at a blistering 10 Gigabits per second. This is double the theoretical maximum of the relatively new USB 3.0 protocol, and orders of magnitude beyond previous transfer protocols. More importantly, early feedback from final design products indicate that the 10Gbps is a usable amount of bandwidth - not a merely theoretical maximum speed.
This has clear implications for today's ever growing amount of data, particularly in business and scientific research, but it also has a very important application in consumer technology. While USB 3.0 is fast, perhaps faster than a majority of computer users ever typically need, Thunderbolt's bandwidth exceeds the throughput of a typical PCIx16 bus. What this means is that external graphics cards are finally a feasible consumer product, as the connection to the motherboard over Thunderbolt is just as fast - and potentially faster - than most PCI bus connections (which seem to range in the area of 4-7 Gbps depending on the individual hardware configuration). Replacing a video card on a desktop machine is a pretty painless project, but upgrading the graphics of a laptop is all but impossible - let alone for those lacking discrete graphics to begin with.
Many companies sell laptops capable of gaming on the go, but the truly capable machines are often quite heavy - and very low battery life at load - limiting portability. Imagine this: a super-thin laptop with basic integrated graphics on-board for portable use, but a high-powered GPU for gaming at home (either feeding back to the laptop screen or driving an external monitor or HDTV. Using Thunderbolt, this is a viable arrangement, and the DisplayPort connector makes connecting an external GPU "in line" with a display practically seamless.
According to this rumor, Sony will be the first to offer a discrete GPU solution for an ultraportable laptop. In this case, it takes the form of a docking station which provides what they call a "hybrid PC" experience, but standalone upgrades from GPU designers could be around the corner depending on how closely Intel licenses its technology (since the company does have a vested interest in graphics processors, albeit integrated ones).
Image source: Ars Technica