I think it does a bit more than that.
Looking at the description of Improvised weapons in 5b (p. 46), you get your proficiency bonus if the improvised weapon looks like a weapon, but not if it doesn't (wagon wheel, dead goblin).
So the feat is giving the player:
* stat bonus to Str or Con (good for odd numbers)
* proficiency in unarmed strikes for Rogues and Wizards (so sneak attack with fists now possible, which frankly by itself makes taking the feat worthwhile!), and damage ~ dagger.
* proficiency bonus to ANY improvised weapon (which in turn should authorize the DM to be less forgiving with creative justifications, etc.)
* bonus grapple action.
Is it mechanically optimal? Probably not, but the idea of a brawling rogue half-orc is pretty appealing to me.
Rogues can only sneak attack with finesse weapons so no sneak attacking with unarmed strikes.
This feat would never get used as a primary form of combat, if you want to be an unarmed fighter you play a monk, since it won't get used very often it is not worth spending a feat on. If the feat doesn't come up almost every round of combat it is not a good investment.