Long short story, I made an app that fits my needs to keep myself up to date on AtCoder and Codeforces contests (the listcould be improved in the future), and I'm glad to show it to you, ContestsReminder.
Features: - Real time notifications when new AtCoder or Codeforces contests are registred. - Hide contests. - Individual contest notifications (if enabled for each one) between 1 hour and 1 minute before that contest starts.
As always, feel free to leave feedback, make a pull request or whatever you like.