here and the Android app here. However be warned, the push notifications can be too irritating.
here , the Android app here and the Windows Phone app here
Google has added a lot more than just score-tracking with this latest update. You can view the different groups, line-ups as well as the main events that have happened during the match. Minute by minute coverage is a welcomed change, and with this also being a voice assistant you can ask "When does (insert team name here) play next?" or "What was the score in the (Team 1) vs. (Team 2) match?" The best part is that you can view all of this if you just search for the World Cup on your PC or Laptop. You can click here if you want to view the current match score or what matches are coming up. For iOS, click here. If you're on Android (4.1+) and Google Now didn't come bundled with your phone or you want to check for an update you can do so by clicking here
At the end of the day, whichever app you install you can't really go wrong. If you are looking for a more detailed app that offers extensive coverage, I would either recommend the FIFA or Onefootball Brasil. If you want a basic app that allows you to check the score quickly, I would recommend Google Now.