I stumbled across this video on a release device for anchors that are stuck on an object. I know that people use Plastic ties and other weak link items to put into the anchor chain. The selling point seems to be that you can adjust the breaking point of the link. I looks like this item is sold mostly in the UK and or sold on ebay. I'm not sure of this has already been posted and if so sorry for being late to the party.
http://youtu.be/BYuUksj0L3c
http://youtu.be/BYuUksj0L3c
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