A few days ago, the latest version of the iOS 9 beta was released and it has brought some innovative stuff. Among them is the new Wi-Fi Assist feature, it will recognize bad Wi-Fi connections, and use your cellular data instead.
You can always switch it on and off with a toggle in Settings, so if you’re confident in your home Wi-Fi or you want to avoid using your cellular data because of the limitations, you can disable it. If you just toggle it on, it will detect when you’re using a network with crappy speeds or no connectivity at all and toggle your cellular data instead. Before it uses your data, the Wi-Fi signal will turn to gray, giving you ample notice that you are about to use your data in browsing.
Other features included are a new set of wallpapers, and other bug fixes from the previous beta.