My house rules have always been as follows:
A monk may make an attack with any object or none at all, but it is resolved in ALL WAYS as an unarmed attack. Even enhancement bonuses on weapons don't count. This makes it merely a flavor distinction. However, once this rule is in place, feats become available:
Extension of the Body
Prerequisites: Improved unarmed strike
Benefit: When a character uses any object in place of an unarmed strike, he deals the kind of damage appropriate to the weapon, such as piercing or slashing. If a weapon deals some kind of energy damage, roll unarmed damage normally and divide it evenly among the physical damage and all forms of energy damage. Rounding goes to physical damage. In all other ways the attack still functions as if the monk had made an unarmed attack.
Clever Improvisation
Prerequisites: Improved Unarmed Strike, Extension of the Body, Base Attack Bonus +4
Benefit: When a character uses an object that provides reach or a bonus to disarming in place of an unarmed attack, he may use its extra features by reducing the size of his unarmed damage die by one. d20 becomes d12, d3 becomes d2, and d2 is reduced to 1. He must make this decision whenever he picks up a particular object, and is bound by it for that particular object thereafter, though not the type of object. For example, if a monk picks up a ladder and uses it to gain a reach advantage, that ladder must always be used as a reach weapon. If he picks up another ladder, he makes the designation then.
Quick Change
Prerequisites: Improved Unarmed Strike, Clever Improvisation, Quick Draw, Base Attack Bonus +4
Benefit: The first time you switch weapons in combat you gain a free feint attempt against your next opponent. If you beat him, the next time you switch weapons you may feint again as a free action. You may continue doing this until he beats your feint check.