AGT: America's Got Talent is an official, NBC-sponsored app that lets you participate in the hit reality TV show America's Got Talent in your own way. You can use it not only to buzz in, but to talk on social media about what's going on the show. There are even live voting episodes on the show which are specifically meant for playing along in this way! There's a few other features that might interest fans of the show, too...

Green, red, and gold (not yellow)

AGT: America's Got Talent is a gateway to participating in the show, which previously was limited to those using SMS or, earlier, those who were physically present to watch the show. Now, you can give a "yay" or "nay" to the various acts that are performed on the show, or even signal that you think someone's worthy of the grand prize, with three colors of buzzer: red, green, and gold. The app is updated for every new show, and your responses do matter.
Notably, you can use your buzzer even if the show isn't currently airing. This makes it easier to keep up with it if you have a busy schedule, or are working and watching while the show is on, for example. Though you won't be "playing along" with the rest of America at the time, it's still a useful feature that can make using the app easier.
The app also provides Facebook and Twitter integration. You can tweet about your favorite acts and how you voted, and even tweet the contestants and judges directly from the app, if you so choose!

Watch what you're doing

The app's interface is well-designed and works quickly. There's not much else to say here: aside from a brief delay while the sound plays and you buzz in, there's nothing bad to be said about the app's interface!
Unfortunately, while the app is great at what it does do, there's a glaring omission here. You can't actually watch episodes of America's Got Talent via the AGT: America's Got Talent app. You can save acts on results nights, though. Although this is reasonably common for all kinds of apps that hook into an existing TV show or channel, it's still an unfortunate omission. Even being able to view the most popular clips from the show would be a welcome addition, for casual viewing, for sharing with friends, or even deciding how to do vote.

Reasons to buzz in

Basically, this app will be useful to you if you enjoy watching America's Got Talent and want to participate a bit more easily. As ever though, remember that the judges have a huge amount of sway over the game, compared to individual voters. So don't be too bitter and blame the app if your preferred winner doesn't win!
Though you can't view any content from the show itself with AGT: America's Got Talent, this app provides a great and easy way to participate and a bunch of feelies that make it all work together.