You're looking for a Cydia app to download YouTube videos. Here are a few options:
(Cydia app): Another option is this app, which allows you to download YouTube videos in various resolutions. cydia app for youtube video download
(Cydia app): This app allows you to download YouTube videos directly to your iOS device. You can find it in the BigBoss repository, which is one of the default repositories in Cydia. You're looking for a Cydia app to download YouTube videos