Beluga Shipping and KiteSails teamed up to have a 160sq/m kite help pull the ship, cutting as much as $1600 from fuel costs per day. Interesting stuff...
http://www.reuters.com/article/inDepthNews/idUSL1548100520071217?sp=true
http://www.reuters.com/news/video?videoId=72795&newsChannel=inDepthNews (video, has some good images)
http://www.networkworld.com/community/node/22225
I think if one were planning a tradewinds passage, having a big kite rigged would make a lot of sense. For the singlehander, it should be much easier to fly than a spinnaker, at least! :)
Kinda on the topic of a 'return to commercial sail' in the great internal combustion era, I read a VERY interesting article in OCEAN NAVIGATOR years back.
A dude was contracted to rig an oil platform for sail to lighten the bollard loads on the tugs for a passage. The rig was triangular, so he put three masts - one on each corner - and used whichever combination of sails was suitable for wind conditions. Most of the trip was made with near-zero on the bollard strain guages, proving that you CAN sail a triangular oil rig (probably about as unseaworthy 'ship' as ever was contrued) on a long passage. The tugs essentially idled across pulling their own weight, only 'tugging' at the ends of the trip.
It was utterly fascinating when I read it.
Back to flying kites .....
Now thats the ultimate motor sailor. ;D