Stunning Fist isn't really powerful, but it's far from awful. Targets the most commonly high save, granted, but the DC is respectable, the effect is powerful to inflict on someone, and there's no cost in actions to use it. Further, can't think of many feat or abilities that improve it much...
Ring the Golden Bell to make melee attacks at range, but I'd rather just have an ally to cast Blood Wind if possible.
Some pressure point feat to let you burn more uses for healing, paralyzing and other exotic effects, is sort of nice but hardly mandatory.
Only straight-out power boost feat I can think of is Pain Touch, so the round after you stun the foe, he's nauseated (ie, you rob him of two rounds of actions instead of just one).
Grappling, on the other hand...I think Imp. Grapple is the better feat for monk dips, but for straight monk? You're getting medium BAB and too much MAD to have as high a strength as the Fighter. RAW, I don't think you can use flurry of blows in a grapple (I allow it, but I recall that being a houserule). I'd argue monks really aren't that good at grappling without lots of extra feats and items to aid in it. Sure, it's nice at low levels to pick on mages before they get the ability to Dim Door or use Freedom of Movement (of course, Abrupt Jaunt and Benign Transposition from splat books are open right from level 1...), but the casters aren't much of a threat at thos levels anyway. And if you can swap it out later on, nothing's stopping you from just picking up Improved Grapple with a regular feat. Later levels, the Fighters have much better str and BAB than you, the casters are grapple immune, the rogues...it sucks to be a rogue..., the monsters are frequently massive with unbeatable grapple mods... Just saying.