you know what

Phrase

idiomatic

(idiomatic) A phrase used to get someone's attention before announcing something.

Japanese Meaning

相手の注意を引き、これから重要な情報や本題を伝えるための口語表現。 / 聞いてほしいことがある前に使われる、話の前置きとしての表現。

I'm packing for the trip and you know what, I think I'll bring my guitar.

旅行の荷造りをしているんだけど、ねえ、実はギターを持って行こうと思う。

Sense（1）

(idiomatic) A phrase used to get someone's attention before announcing something.

Well, you know what, he's got a cloud over him. You have to live with who you are and make your peace with your maker about what you really are.