The program works via a pseudo-Youtube-interface, so one can download a video via WiFi with a high quality setting or a lower quality setting via Edge.
In order to install MxTube and download YouTube videos onto your iPhone, you need to have a jailbreaked iPhone with Installer.app on it. Make sure you have “Community Sources” added, then locate and install the program.
To install, find it from Installer’s “Multimedia” category and to download, run a search as you normally would and select the video you want to download. As YouTube has two versions of every video, high and low quality for downloading it you can select high, low or both. The videos will download in sequence and in the background. Once it's done downloading, the video is available from within the application.
The MxTube application searches and saves YouTube videos directly to your iPhone or iPod touch so you can play them back at any time, whether you've got an active internet connection or not.