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FYI, Steam has had a built-in one for a while now. Go to Preferences-->In-Game.
Last time I checked, you can see the current frames per second, but you can't get an average / max / min from the session. Has that changed?
 
Can't get that app working. Tried it on Talos Principle on Steam, got some kind of PID error, then looked at the Help section, clicked on Wait, then launched the game, and still nothing.
Then tried Limbo by adding the game into the Count It menu, clicked on Launch, a '0' appeared in the bottom left corner, and never changed!
Don't really know what's going on.
 
Can't get that app working. Tried it on Talos Principle on Steam, got some kind of PID error, then looked at the Help section, clicked on Wait, then launched the game, and still nothing.
Then tried Limbo by adding the game into the Count It menu, clicked on Launch, a '0' appeared in the bottom left corner, and never changed!
Don't really know what's going on.

That's strange. Are you running El Capitan? Also, did you try to add the game by "platform"?
 
Yes, I'm on El Capitan.
Limbo works now OK, don't know what was going on yesterday.
I think I see the problem with Steam games. Count It doesn't list all the Steam games and the ones that aren't listed don't work.
Also, I've noticed that even when it is working, it seems to cut off after a minute or so on occasions.
 
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