You can download Tubemate YouTube download apk at mobango. I downloaded it from the site to my Blackberry q10 and it has been working fine for me since then. The app simply allows you to search and save youtube videos on Blackberry 10 smartphone.
Because downloading always happens in the background, you can go on watching YouTube, surfing the Internet, tweeting, and listening to your music as you download. All your download videos appears in a list and you can even play the videos as music and also add them to playlists.
The Tubemate YouTube downloader application also works perfectly for Android phones.
You can check more mobile sites for phone downloads here.