Yaniv Pessach is asking for exotic WCF channel ideas to follow on from his Carrier Pigeon channel. I'd like to suggest a mailboat channel. Even slower and less reliable than pigeons but also based on a tried and tested technology.
A St Kilda mailboat is a wooden 'boat', containing a letter, usually sealed in a cocoa tin. A sheep's bladder acts as a float. The first mailboat was sent out as a distress signal in time of famine by John Sands, a journalist, who was stranded on St Kilda during winter of 1876. It was later used by St Kildans as a tourist gimmick.
Mailboats are now sent by St Kilda work parties as part of the ritual of visiting St Kilda. They are carried by the Gulf Stream and usually reach land in Scotland or Scandinavia. Records of mailboats, and where they were washed up, are published in the St Kilda Mail.
A recent mailboat sent with greetings to the new Scottish Parliament arrived within a few weeks!
 WCF = Windows Communication Foundation