Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.
I bought the Halo ones out of curiosity because of how cheap they are.

You apply them to your iPhone without any liquid, or at least that's how I did it. It has a 2 step process. You peel a sheet off the protector, you put it on your iPhone just right (it's easy as it doesn't cling everywhere like the others). Then you peel off another sheet off and the protector stays on the phone.

I don't think that they are going to last as long as the other type of screen guards, but for the price, it's worth checking out and see if it works for you. It's crystal clear and, to me, it had no noticeable effect on the touch-screen responsiveness.
 
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.