Did you make a typo, Pauline? I'd say only the future continuous works here. You can say I'm coming tomorrow or I'll be coming tomorrow - I'll be there tomorrow. But with I'll be waiting for you at 11:30, there's the idea that I'll start to wait before 11:30. There isn't the idea that I'll start to come.It's the present continuous you need here.
"I'm waiting for you at 11.30" would only make sense if, say, it was exactly 11.30 and you were texting the other person because they were late.