Text on center of menu bar
AnyBar with Text should do what you want. I have used the project it is forked from (AnyBar) to successfully monitor things.

This free app runs in the background and there are a variety of ways to issue it commands, including from the command line, AppleScript, or through programming languages like Go, Node, PHP, Ruby, Java, and Python.

Edited to add: Note that the text won't be in the center of the menubar, per se, but it will be toward the "inside" of the status icons on the right hand side, towards the middle.