text element mixed coordinate systems

Hi...I'm interested in plotting text elements with the X value in data coordinates and the Y value in axis coordinates (in this way I could plot labels at the top of the axes that would respond to zooming/panning in the X-direction but would *always* remain at the top of the axes as long as the X-coord was still in the axes, for example). Is this possible?

Also, it seems the only differences between axvline and vlines are that vlines can take multiple lines as input and vlines uses data coords to set the y limits while axvline uses axis coords. It seems simpler to have one function that takes an optional argument to choose whether to use data or axis coordinates for the y range (and maybe even for the x value...ie producing the same functionality that I seek above).

Thanks for any help/suggestions!