Mouse is a small draggable windoid that shows horizontal and vertical coordinates of the mouse cursor relative to screen and to front window. It registers changes in coordinates when moving the mouse with the option key. It also shows red/green/blue color values of screen point directly underneath cursor. Data can be copied to the clipboard.
Version 2.0 is completely rewritten. Window genuinely floats, without interfering with your work. Window can appear in vertical or horizontal position. Will float above all applications or above any specific application, hiding when that application is not in front. Dismissed with a click in its close box.
System 7.5 or later, Akua Sweets, Dialog Director and Jon's Commands scripting additions (all free for personal use).