Tube Buddy

If you need to review segments of YouTube videos for educational purposes, then this app is for you.
Besides allowing you to repeat segments of a video, you can also define any number of "tags" per video that you can come back to and replay. Great for long instructional videos where you need to review each segment over and over.
Instructions
To switch between the "Controls" and "Tags" views, use the grey button in the upper right corner of the screen.
Controls View
Red Button - Allows you to view a YouTube video by specifying it's URL. You can get these URLs from the "Share..." or "Copy URL" options of the YouTube app. Another method is to simply select Tube Buddy from the list of apps in the "Share..." list of the YouTube app.
Green Buttons -Allow you to seek to the star of the segment or video, play or pause, seek to the end of the segment/video, seek backwards far, seek backwards short, seek forwards short, and seek forwards far.
Blue Buttons - Allow you to set the start of a repeating segment, set the end, clear the start of a segment, and clear the end.
Tags View
Green Button - Allows you to create a tag at the current video position.
Blue Buttons - Allow you to rename the associated tag.
Red Buttons - Allow you to remove the associated tag.
Touching the label of a particular tag will immediately start the related video segment and play it continuously in a loop.
Permissions
Requires "network status" and "internet" permissions to playback YouTube videos and display ads. No other permissions required.