AutoCAD Civil 3D contains also functions of AutoCAD Map 3D and so you can find here two similar functions for live tracking of cursor coordinates - the dialogs (palettes) "Coordinate Tracker" and "Track Coordinates".
The newer, Civil-oriented functionality especially for 3D surfaces is included in the "Coordinate Tracker" - the lower palette on the picture:
Besides the X,Y coordinates of the point beneath the cursor, it show also the Z-coordinate on the selected terrain surface. You can invoke this palette using the SHOWCT command (and hide with HIDECT), or from the ribbon with View > Palettes > Coordinate Tracker.
Besides interactive display of coordinates you can also capture coordinates (Ctrl+Shift+Z by default), after this you can edit or copy the coordinate values (restore live display with the right-arrow icon), or you can use the obscure button-bars below the coordinates to copy the current values of XY, Z or XYZ coordinates to your command line.
On the other hand the second tracker is intended for surveying/GIS functions in Map (the upper palette). You can ivoke it (and hide) with the MAPTRACKCS command or with the function Analyze > Geo Tools > Track Coordinates in the ribbon of the "Planning and Analysis" workspace.
You can "breed" the tracking display in many coordinates systems by adding new panels (through the "+" in titlebar). The tracker will show lat/long values of the point under cursor in multiple coord.systems at the same time - if the coordinate makes sense in a given coord.system (try to change your CS using MAPCSASSIGN).
With settings (hover on the panel title) you can also change formatting of the coordinates (decimal number vs. DMS, grid square):