I always keep Videoder & OGYouTube on all my devices, but the one that I end up using the most & has proven to be most reliable is YouTube Downloader. Its browser isn't the best, but the way I use it is to share a video from a separate app. Works great for background downloads.
It also has a built in tagger which is accessible after a file has finished downloading.
I don't know about all your other requirements, but I share videos directly to the following app. I doubt you'll find one without any kind of interface.
YoutubeDownloader works well for me: http://dentex.github.io/apps/youtubedownloader/
After installation, you use the 'Share' services to access the app. Works great on browsers (desktop and mobile pages of YouTube) and in the regular YouTube player. You get a list of available video formats/resolutions.
YouTube Downloader for Android
Not the fanciest, but it lets you download in different video qualities of available, and extracts audio into mp3 files.
If a video can be played, it has to be sent. If it can be sent, it can be intercepted.
They "can" encrypt it, but it has to be decrypted at some point, to play.
Aka, if you can see it, it can be downloaded.
Also, I don't rec web sites for it. On Desktops, I use VideoDownloadHelper as a browser extension. On Android I use Youtube downloader. Works great, and they are both better then sites.
> without having to go to another site
Would you be ok with going to another app? YouTube Downloader for Android Just press share in YouTube and select the app.
On the off chance you are an Android type of dude/dudette this little app is great for downloading YT videos or extracting mp3 audio from them: http://dentex.github.io/apps/youtubedownloader/
If you're an iPhone feller/lady Apple hates you (there are iOS apps that can do this, but you have to catch them before they are taken down and then never update).
For the desktop something like this? http://www.youtubedownloaderhd.com/youtube-to-mp3-converter.html
Android users can use uListen to stream audio from YouTube videos. I listen to lectures, Google talks, tutorials etc.
There's also YouTube Downloader which let's you download the audio stream as an .m4a or .ogg for playback later. It's not available in the app store, but the .apk is here: http://dentex.github.io/apps/youtubedownloader/
I've been using YoutubeDownloader: http://dentex.github.io/apps/youtubedownloader/
After installation, you use the 'Share' services to access the app. Works great on browsers (desktop and mobile pages of YouTube) and in the regular YouTube player.
Update: I just installed Dentex youtube downloader from your link (full url for posterity: http://dentex.github.io/apps/youtubedownloader/ )
It works like a charm. You don't even need to use the youtube app. You can search right inside youtube downloader, and convert the audio/video to the format you choose.
EDIT: Again, thanks!
Good point, I don't personally use TubeMate but I've had it recommended to me. After I did some quick research on TubeMate, the permissions definitely seem fishy, and they aren't explained anywhere on the web. I think you should use YTD (Youtube Downloader) as a better alternative to TubeMate.