A simple phone call and high-level discussions could do a lot to help with the North Korean issue. Dennis Rodman, upon his return from Nortk Korea, indicated that a phone call from President Obama to Kim Jong-un would do a lot of good. Video here: http://www.bbc.co.uk/news/world-21650642.
The signers of this petition believe that diplomacy is the best way to handle any type of foreign issue, and President Obama making a simple phone call would have the most impact with such a small cost in terms of money and the President's time.