An attention-getting phrase used to tell someone to listen closely (colloquial).
いいか、明日の集合時間はいつもより早いから忘れないで。
Listen: tomorrow's meeting time is earlier than usual, so don't forget.
いいか、こっそり持ち出したら絶対にバレるぞ。
Okay, listen — if you sneak it out, you'll definitely get caught.
いいか、実験中は指示を守って動くんだ。
Listen: follow the instructions during the experiment.
A colloquial phrase used to emphasize a point or remind someone (meaning like 'mind you' or 'remember').
いいか、無理はするな。本当に体が大事だぞ。
Mind you, don't overdo it. Your health really matters.
試験は来週だ。いいか、最後まであきらめるなよ。
The exam is next week. Remember, don't give up until the end.