A fighter using unarmed attacks (guess that's what you mean) can use bracers and an amulett of mighty fists.
I don't know if they stack but I guess so as the one has armor enchantments on it and the other one weapon enchantments. As far as I know.
Enchantment bonuses definitely will not stack as covered under Bonus (Enchantment). It doesn't matter how many effects give you a +1, you still only have a +1. The abilities of each should stack however such as holy or keen. Just as if you had flaming arrows and a shock bow, you would now have flaming, shocking attack. If this seems too good, I would advise the unsure to look at the ridiculous prices for the Amulet of Mighty Fists and remember that it takes the precious neck slot away. So my two copper says that RAW would rule no for enchantment bonuses and yes for abilities.