I believe that the functionality you need is the one described in this
blog post. I have modified slightly the project. You can review the attached file.
Basically I changed the LayoutRoot from Grid to Canvas (so I can position freely objects inside of it) and on MouseMove set the Canvas.Top and Canvos.Left attached properties of the infoText to the coordinates given by the MouseEventArgs.GetPosition(). Also the 2 TextBlock-s (that display the coordinates of the mouse pointer) are hidden and shown on MouseLeave and MouseEnter respectively.
I hope this is the solution you are looking for.
the Telerik team