This is used by a lot of PLDs attempting to make up for the lost stats from Gluttony Sword. They're making a mistake with this, though. For one, there's no VIT or enmity at all. Two, Life Belt provides much needed accuracy to PLD, a very innacurate job as it is.
The usage for this belt is actually for macro in with Weapon Skill. It will provide temporary modifier boost. This belt covers almost every Weapon Skill there is because no weapon skill have VIT modifier. Except for a few odd apples like Spirit Within or Atonement, which have HP and Enmity modifiers, respectively. Unless you have multi-hit weaponskill that heavily relied on accuracy, this is very good belt. In general situation, Life Belt and Swift Belt fare much better.