Touch attacks are armed melee attacks which use the body and bypass armor and shield AC bonuses.
Unarmed Strikes are also an armed melee attack which uses the body. However, they are a different type of armed attack, and as Bob has pointed out, bonuses to one type won't help another.
You can, however, choose to make a normal unarmed strike (versus regular AC) and additionally deliver a touch attack at the same time. See Holding the Charge. In this case, you could use Guided Hand.
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However, I do have a minor nit-pick with Bob's comments: The Amulet of Mighty Fists' enhancement should probably apply to combat maneuvers such as grapples.
From a paizo blog:
Quote:
Page 199 of the Pathfinder RPG Core Rulebook says, “When you attempt to perform a combat maneuver, make an attack roll and add your CMB in place of your normal attack bonus. Add any bonuses you currently have on attack rolls due to spells, feats, and other effects. These bonuses must be applicable to the weapon or attack used to perform the maneuver.” That last sentence implies that some weapons apply their bonuses on combat maneuver checks, and some do not. So how do you know which weapons do? The answer depends on what kind of combat maneuver you’re attempting, and in some cases what kind of weapon you’re using.
Disarm, sunder, and trip are normally the only kinds of combat maneuvers in which you’re actually using a weapon (natural weapons and unarmed strikes are considered weapons for this purpose) to perform the maneuver, and therefore the weapon’s bonuses (enhancement bonuses, feats such as Weapon Focus, fighter weapon training, and so on) apply to the roll.
For other maneuvers, either you’re not using a weapon at all, or the weapon is incidental to making the maneuver and its bonuses shouldn’t make you better at attempting the maneuver. For example, just because you have a +5 greatsword doesn’t mean it gives you a +5 bonus on dirty trick checks (Pathfinder RPG Advanced Player’s Guide 320), and just because you have a +5 dagger doesn’t mean it gives you a +5 bonus on grapple checks. Of course, the GM is free to rule that in certain circumstances, a creature can apply weapon bonuses for these maneuvers, such as when using a sap in a dirty trick maneuver to hit an opponent in a sensitive spot.
To sum it up, as long as the type of weapon is appropriate for making the combat maneuver, you can apply any enhancement bonus on the weapon.
Granted it is GM discretion, but I believe most would agree that unarmed attacks are an appropriate weapon for grappling, and thus would benefit from AoMF's enhancement bonus.
