There is no catchall setting on iPhone that will block explicit content across all content providers, so if you don't want your kids watching rated R movies or listening to explicit lyrics, you're going to have to block it on each service you subscribe to.
Instead of TV shows and movies consolidating under the umbrella of a single source as many of us once hoped for, there has been an explosion of original content from a plethora of sources that keeps us picking and choosing our subscriptions à la carte. Some of these providers let you download content to watch offline, some don't, and some charge extra for the service.
Hulu fans can consolidate more streaming content thanks to a deal between Hulu and HBO. Subscribers to Hulu with any monthly plan can add Cinemax to their package for $9.99 or HBO for $14.99. This matches the pricing for HBO's stand alone HBO Now app, which brings all of the network's content to mobile devices.
There is no way to sign up for an HBO Now account online unless you sign up through an internet or mobile provider. You can see a list of providers here. This page also provides links and instructions on how to sign up for an account through each individual provider.
The easiest way to sign up for an HBO Now account is through one of the official HBO apps on your iOS or Android device, or via a digital streaming service, such as Apple TV or Roku.
HBO today has officially ended its exclusive deal with Apple by updating its NOW iOS app with Chromecast support. Version 1.2.0 of the HBO NOW app allows Chromecast users to cast HBO original series, movies, comedy specials, documentaries and more to their television sets. Originally HBO NOW subscribers could only stream HBO NOW programing using Apple devices, such as an iPad or Apple TV.