As a PSA on XO Skins for runners...
First off, I've used a ton of screen protectors on my smartphones over the years and XO is the best, IMO.
But, unlike the other protectors, XO *will* interact with plastic that it comes in contact with. I use a Tune Belt armband when running, and the XO stuck to the plastic window in the armband and deformed when separated. Other brands did not do this.
If you plan on using an armband with a plastic window, consider turning it around, so the XO does not come in contact with the plastic.