This app was mentioned in 3 comments, with an average of 1.67 upvotes
LOLsummoners - detailed information on summoners, champions & counterpicks and items, with matchhistory, ranked stats, ...
https://play.google.com/store/apps/details?id=com.lolsummoners&hl=de
I use LOLSummoners. As far as I know it stays relatively up to date with champion stats, and it's a really well-designed app too. It also includes items, the free rotation, and lets you look up summoner profiles.
This is a very valid point and something I considered when first monetizing the app. Perhaps this is a misread on my part but I took this to mean you directly mean "your app must be free and you can't sell League related content."
While I do have a purchase for advanced features it's for deeper analytics into the freely provided statistics of your performance. Everyone can see the basics offered, e.g. games played, champion stats, league info, live game info, but if they want a more visual breakdown that's where I provide the in-app purchase. All of the information in this purchase is already visible to the free user just in a different form.
I know this isn't necessarily justification that what I do meets guidelines but there are many apps out there that profit indirectly off of the API like I do. Here are some examples:
https://play.google.com/store/apps/details?id=com.lolsummoners
https://play.google.com/store/apps/details?id=com.telesoftas.lolspy
https://play.google.com/store/apps/details?id=com.salsalol
I've also messaged Riot about several technical issues in the past few months to which they've been very helpful and at no point did they event mention the in-app purchases being an issue and my account is still in good standing on their development portal.
Thanks again for looking even deeper into this, I really appreciate it.