p182 of the CRB lists the following types of attacks as 'armed' unarmed attacks: a monk, a character with IUS feat, a spellcaster delivering a touch attack spell, and a creature with natural physical weapons.
Since it is grouped in with monk attacks and IUS attacks, this would lead me to believe that touch spells benefit from an Amulet of Mighty Fists. Nowhere else in the 'Attack' section of Standard Actions does it discuss spell touch attacks.
p185 of the CRB describes touch spells as 'an armed attack'
This would lead me to believe touch spells do NOT benefit from an AoMF.
Everything I've read elsewhere on the forums, as well as my gut reaction and the general accepted play I've experienced with every iteration of tabletop gaming, says the latter of the two is the correct interpretation.
However, I'm trying to go strictly by RAW. I can't find Errata changing or correcting the first statement, or a satisfactory explanation of why 'armed' unarmed is used to describe Monk attacks, IUS attacks, touch spell attacks, and natural attacks, but one of those four listed doesn't benefit from an AoMF. The context of the first statement on p182 feels like a further clarification of the 'Attacks of Opportunity' section, but there's a significant amount of ambiguity in my mind.