Get the Z position of a 3D surface under the mouse pointer

[Mark81]

Is there, or it's even possible to write, a plugin that shows the Z position of the 3D surface as the mouse moves? In the status bar there are the X, Y mouse coordinates, I would like to know how deep is the surface at that point.
The best would be a real-time update of this value, without have to "ask" for it (like get object extremas for example).

[EddyCurrent]

There is now 
http://www.cambam.co.uk/forum/index.php?topic=7631.msg61246#msg61246

[Mark81]

Wow, great! But I'm having some weird behavior with version 1.0.
When I press 'z' nothing happens, but if I press it several times then a zpos appears. Other few 'z' press and another measurement is made, but after a couple of messages it "cycles" among them. I mean it doesn't append another message, but it just highlights a previous row.

Please let me know if I can try something specific so my feedback might be more useful.

[EddyCurrent]

Keep z pressed all the time, do not keep releasing it, and move the mouse over a surface.

[Mark81]

Ok, now I get consistent readings, but the last problem is it takes a lot of time to make a measurement (about 1 per second) hence when I release the key, it continues to show messages for a lot of time! I'm afraid it's because it tries to make a measurement for each "key press/repeat" event and appends them all in a sort of queue. When I move the mouse it takes 10-15 seconds before it returns the actual value under the current position!

I think it would be better if the plugin starts a new measurement only when the previous one has completed, using the updated mouse coordinates read at that moment.

[EddyCurrent]

You should have Tools->Options->Display Mode = OpenGL otherwise it sounds like you may have a slow computer.
In any case the values are updated only when the mouse is moved, so if you move the mouse slowly, that should solve your problem.