How to display 'Elapsed Time' (since activity start to now)

Summary: We would like to display the ELAPSED TIME (in minutes or in hh:mm format) since the activity was started.

Content (required): The elapsed time should be calculated based on actual (current) time and updated each time the screen is accessed. In a perfect world the elapsed time value would update LIVE (as the user is looking at the screen) but I doubt that is possible. If it could at least update each time the screen is accessed (opened) that would be good enough for our need.

Version (include the version you are using, if applicable): 23B with service update 8.