I bought one of these because I'm doing a kit wine and gravity readings are very critical to the process.
This thing is so cool. The hydrometer goes into the wine thief and you can quickly check the gravity then pour the liquid back into the fermenter. You must of course sanatize the thief and the hydrometer.
I'm thinking this could work good for beer too. I never test my gravity unless I'm racking the beer. Now I'm thinking about testing it before I rack to be sure it's where I want it.