There are relevant materials at two websites:
BSA - http://www.scouting.org/jamboree/sitecore/content/Home/International/messengersofpeace.aspx
World - http://scoutmessengers.com/index.html
In looking through the materials on both sites I found myself really stirred by this initiative. The goal is essentially to "help Scouting create a better world."
|MOP emblem - from BSA website|
Scouts who want to participate simply do service under one of three dimensions (personal, community, or environment) that promote peace. There is no approval necessary--the unit decides whether or not the service qualifies. Service hours are entered into the Journey to Excellence website (https://servicehours.scouting.org/UI/Security/Login.aspx) and those who participate are eligible to wear a special ring patch around the World Crest on their uniform.
I see this patch as less of a reward for doing service (or bribe to convince boys to do it) and more of a reminder about what Scouting can and should be. It's a symbol of a Scout's commitment to "help other people at all times" and to be "a friend to all" and "a brother to other Scouts." It's a reminder that through a simple good turn a boy can make a difference in the world.
As a member of the Church of Jesus Christ of Latter-day Saints, and someone who claims to follow the Prince of Peace, this really resonated with me.