T-Bone said:
The written rules may be against me here if I track down that ""Flurry of Blows" attacks are either "unarmed attacks" or "melee attacks with a monk weapon", and that an "unarmed attack" can be used to start a grapple.
Well, Grapple has a footnote on the Table of Action types, along with Trip and Disarm, as follows: "These attack forms substitute for a melee attack, not an action. As melee attacks, they can be used once in an attack or charge action, one or more times in a full attack action, or even as an attack of opportunity."
Basically, any time you can make a melee attack, you can grapple instead.
Flurry of Blows notes: "When using flurry of blows, a monk may attack only with unarmed strikes or with special monk weapons."
... huh. You know, I'm going to change my position on this one.
"Unarmed Strike" is distinct from "Grapple", as evidenced by the fact that there's a different Weapon Focus applicable to each.
Anything that grants "an extra attack" can be used to Grapple... but since Grapple is neither an "unarmed strike" nor "a special monk weapon", a Grapple check cannot be part of a Flurry of Blows.
A monk who is already Grappling could use Flurry of Blows to attack with an unarmed strike or light monk weapon repeatedly... but he couldn't mix in any of the other grappling actions, just as he couldn't mix in an attack with a dagger.
Trips or Disarms made with unarmed strikes or special monk weapons would still be a valid part of a Flurry of Blows, since they use the Weapon Focus: Unarmed Strike (or whatever). But Grapple doesn't, and as such is not eligible for use in a Flurry.
-Hyp.