If you look at the bike lock in the above photo, you'll see that it's black with white stripes. It's no coincidence that that's the same coloration as a skunk. And, just like a skunk, the Skunklock will make a big stink if anyone messes with it.
Although it looks and (mostly) works just like a regular U-lock, the Skunklock has an interior chamber that runs throughout the length of its hardened medium-carbon steel shackle. Sealed within that chamber is a pressurized legal-but-noxious "unique chemical deterrent."
Under regular use, that chemical stays inside the lock. If the shackle is cut into and the chamber is breached, however, the deterrent gets out. It then creates a cloud of very unpleasant-smelling gas which will irritate the thief's eyes, cause them to have difficulty breathing, and may even make them vomit. Additionally, it's claimed that the chemical will permanently permeate their clothing, ruining it.
They could conceivably just return to the lock-cutting task once the gas has cleared, but the idea is that they'll instead move on after having drawn so much attention to themselves. There's also the hope that upon initially seeing the word "Skunklock," they'll be wary enough of the lock that they'll just leave it alone.
And no, it can't be refilled with more deterrent.
The lock is currently the subject of an Indiegogo campaign, where a pledge of US$99 will currently get you one – assuming it reaches production, that is. The planned retail price is $150.