Trully awsome but under-utilised
I presume Play-Asia are selling the DragonCast third party cables as it doesn't mention a brand, which is what I have.

Games that support this are

F355 - All Regions (hold X&Y to see option in US/PAL versions)
VirtualOn: OT - Japanese/US (again you need to do something to bring the option up for the US game)
Sega Tetris - Japanese Only (it has a picture on the back so as not to confuse with other DC Tetris games)
AeroDancing F & I - Japanese Only (be careful as only certain versions of F and I support this mode.

DragonCast cables are clearly cheaply made and I worry mine will break (reports of reliability problems online). But since you'll have to be very lucky and rich to find/buy the official Sega one, this is the only option.

It really gives a multiplayer experience unlike any other, provided the limited support from what are frankly hardcore games doesn't put you off.

One thing to note, both game discs must be the same region for it to work, although provided you have a modchip/bootdisk it works with all consoles (I have one NTSC-U and one PAL and it works fine).

a few great game supported for it!
there are only 3 games known to support the VS. cable, it's worth it only for F355 challenge!

supported games are: Virtual-On: Oratorio Tangram, F355 Challenge, Sega Tetris (Jap), Aero Dancing F (Jap) and Aero Dancing i (Jap).

A necessity for real Voot fans
I had been looking for a working version of this cable, but had been unsuccessful. Fortunately I heard of play-asia's reliability and ordered this cable to play VOOT. The results are amazing. Just like a real arcade. Order from play-asia to obtain recently manufactured and working cables.