for everyone who doesn't want to use any external scripts, just do this:
Create a new FSM. Then create a new int variable called "Count" and a new string variable called "CountString".
Create a new state and call it "active" (just for the sake of this explanation). Add a GUI Label action to it and use the CountString variable as text.
Then add an IntAdd action and add 1 every frame to Count.
Then add a Wait action and set it to 1 second wait time. Add a FINISHED event and use that in the wait event.
Now you can create a second state which you could call "reset".
Link up the "active" state to the "reset" state, and vice versa (again with a FINISHED event).
In the reset state add an IntSet action and set Count to 0.
Now add an IntToString action and convert Count to CountString.
If you do none of those things every frame, it will fire the FINISHED event automatically and return to the "active" state for another second. There it will count how many frames there are and after a second it will update the string again in the "reset" state.
It's not a perfect setup, but it's easy to setup