If you like sports, and you're a subscriber to one of the many cable providers that offer NBC programming, then NBC's own NBC Sports App will allow you to watch streaming video of live events, from the PGA Tour to the French Open tennis games. You'll also get access to an online coverage schedule for all this, and even more.
Video on demand... if your demands are persistent
There's also video on demand, which lets you watch excellent sports content even when there's nothing going on live. You can also access some region-exclusive programming with the app. Unfortunately, accessing anything can be difficult sometimes. NBC Sports crashes on occasion when logging in, and each time you try to use it, you have to enter in your cable provider information. The interface itself is slow, and although it is seeing some optimization as of this writing, it is still far from perfect. If nothing else, once you're watching video, it's smooth as butter and there's little risk of a crash.
A chaser to your existing subscription
As such, NBC Sports is a perfect app to download if you love sports, have the access, and have a little patience to deal with the app itself as well. There's not many alternatives for watching NBC programming on a non-TV device, so it's worth considering for that alone.