A family of Microsoft presentation graphics products that offer tools for creating presentations and adding graphic effects like multimedia objects and special effects with text.
There isn't a simple solution to this.
First, you need to define what "activity" is. Moving to a new slide? Selecting objects on a slide? Wiggling the mouse?
Then you would have to write a VBA event handler in a .PPTM presentation to capture the event type that corresponds to your defined activity, write a timer that measures the amount of time since the last event, and add a subroutine that changes to the first slide if the timer fires. AI may help you write at least part of this.
Finally, you need to save that .PPTM file as a .PPAM add-in and install it on the computer running the show.
Please post again if you need help with how to do any of these steps.