Frankly, I cannot stand third-party apps and think they bring the whole game down. Why can't you just learn to play the game like everyone else? Supposedly this 3rd party app is allowed but I hope to see it banned. You can argue the information you receive from these apps are available by opening an internet browser and going to OP.GG, but there is a clear difference. The difference is that you are seeing all of the enemy team's weak behaviors at a glance and not discovering them by actually going head to head with them. The devs clearly did not add these features to the game client themselves for a reason.
You have just been placed with a team and, OOOOHHHHH NOOOOO!!!!!, there not up to your standard so what do you do....... constantly try to FF as soon as you are able. How is that fair to the other players on your team or even the other team? The fact of the matter is that 90% of these 3rd party apps give the player an unfair advantage.
If someone wants to do this kind of thing using OP.GG during a match that's fine with me. They will gain inside knowledge but at the cost of switching screens and not paying attention to the match at hand, 20-30 seconds can be pretty costly in League.
"Let the RIOT fist of justice prevail!"