I went to NK in 2011 just to see what it´s like. (PN me if you want to see pictures of the trip)
At the time the group I went with had to surrender their phones on arrival, we got them back on departure.
The travel agency I went with (koryotours) obvisouly goes in frequently, and they managed to actually place a Skype-Video-call from NorthKorea:
Skype Call from Inside North Korea - YouTube
Most interesting trip, but you shouldn´t expect reliable communication at any time. If you need to be available/online you should definitely NOT go!
Rgds, Chrisitan