Don't know how they work but I'm guessing the just stick to the top of the blackhead and yank them out. Some of my pores occasionally get blocked up and have discovered (through boredom in work) that a good strong sellotape yanked off quickly has a similar effect. it's fantastic you can see all the laid out on the tape perfectly as it was in the pore. it's so therapeutic.
They use a water soluble adhesive. When you splash your self with hot water it opens the pores (for a better grip on the blackhead) and when you apply it the hot water also �melts� the adhesive on to the area and when it dries it bonds to the blackhead (as well as the strip) so a quick yank and it should (hopefully) come out!!