Sleep based on airplane mode

[keunes]

I normally switch my phone to airplane mode when I'm off to bed and have pretty irregular sleep times. So in addition to the fixed times, an option to depend activity on airplane mode would be great for me.
In addition, many ppl use airplane mode to save battery, not having the phone vibrate could be helpful as well.
(Also related to #7 and #8, but maybe simpler for user and developer respectively)