Learn English – What does “one” mean or stand for in “Hey, I’m on the way, all right? One.”

In this movie two brothers are talking on the phone:

— Yo
— Hey, Isaiah. Hey, are you going to pick me up, man?
—
You all right? What happened?
— Man, just some skinheads
tripping, man.
— All right, I'll be there as soon as I can, all
right? Taking care of some business for Armand.
[…]
— Look man, I really need to speak to you, man, for real. I got some
sh** to run by you.
— Hey, I'm on my way, all right? One.

[ Urban Justice (2007, Don E. FauntLeRoy) ]

Does that one mean anything outside of this context, is it based on the idiom at one as in in a state of agreement/united in thought or feeling? Or is that more along the lines of see you in a minute but literally one minute? Is it like "copy" or "over" on "military radio", or a binary exit status of some kind inspired by an IT metaphor, is it the equivalent of ok, is it a figure of speech, making the issue be the only one thing on his mind (an exaggeration), just pure styling, or something else?

In so many words is it a phrase, what is it related to and what does it mean?