How to retain absolute gameobject size in pixels no matter the resolution?

Is there a way to scale a 3d Game Object to a specific pixel width and height regardless of what resolution is set?

I'm using the alpha cut-off health bar method as seen in this thread and need to be able to set absolute scale for the objects being used as the meters. No matter what I try I can't get them to scale correctly.

I'm using an orthographic camera for them if that helps any.

What do you need to draw? For 3d geometry (ie Meshes), you typically don't wont to set the size in pixels. But if you do, you can always divide the scale by some factor of Screen.width and Screen.height.

For 2d GUI stuff, you can use a GUITexture (set pixel size using the pixelInset Rect) or GUIText (set pixelCorrect flag).

What about using a GUITexture? I think they can use materials, might be wrong here though.