This kind of things are entirely determined by the context. For example, if I was talking with a friend and just showed him a cool trick on something, the sentence would mean "I'm cool, arn't I?" too. No one can answer it if the sentence is isolated. The sentence is the same as English "Very cool" (過ぎますよ just means "very" or "rather"). Even in this English phrase, it could mean you, it, or even myself, doesn't it. It's all in the context, or what was just said or happened before this sentence.