Google just released its YouTube Go app for regions with slow internet. The beta app works similarly to the regular YouTube Android app but gives the option to download a video for offline viewing.
There is Basic Quality and Standard Quality - around 144p and 360p - no HD quality available. This makes sense as YouTube Go will target users with low bandwidth.
People can even share downloaded videos via Bluetooth to save even more of that precious data although Google has warned that a 15kb security check will need to be performed first.
Click here to get the app though keep in mind that it may not be available in your region.