iTube was release with the name Playtube and offered some limited features. Then the developers 24/7 Apps Ltd. gave it a new twist and launched the App with the name iTube for Android users. The App was so much in demand for its amazing features that due to popular demand it was released on other platforms as well.
Even though this is one terrific App for playing music from online video sharing sites it did have a bit of trouble when it was disallowed from Google Play Store due to policy issue. Well, no points for guessing why, because it allows users to save the YouTube videos they play onto their devices by caching it.
iTube For iPhone/iPad Download
The other main feature is that unlike YouTube App which needs to be on the foreground for you to enjoy your favorite music (What an attention seeker!) with iTube you can play your favorite and then do other activities while it plays in the background.
Even though, iTube was easily available for download on iTunes earlier but due to Apple policy it was removed from the store.
Update: Download iMusic IT from iTunes as a best alternative for iOS.
Now there are ways in which you can run Android iTube APK on your iPhone by using Emulator App which lets you install Android Apps on your iPhone. Please visit apps like iTube for iOS for other resources.
A better way will be to visit some sites which help you download videos from YouTube. Here there will be no trouble from policy violation because you will not be installing any App. A few examples are en.savefrom.net, where you only need to visit the website, enter the link and you will be able to download the video with the quality you desire. Else, if you just want the audio to hear from the video then you can go to another website called www.audiotube.org here you can enter the URL of the video link and the website will convert the video to an Mp3 for your download.