What is Is That You?
1.
A Scottish way of asking someone if they are leaving.
It's 17:00 at the office and Rich is putting his coat on.
Scott: Is that you?
Rich: Aye, that's me.
Alistair: Is that him?
Scott: Aye, that's him.
See
2.
a phrase meaning does one mess around or talk to someone : are they together or talking (relationships wise)
Rich: yo lisa looks really cute today i might talk to her but Is that you
Tim: no she's not with me go ahead bro
See