I recently found this product: The AnchorRescue II which looks like an excellent option for being able to trip your anchor if needed without all the problems of using a traditional trip-line to a buoy (tangles, other people picking it up etc).
It is good that it is a 2nd generation product, there have been others using somewhat similar concepts but this seems to have lasted longer and been improved. I like the fact that once setup you can ignore it until needed. Also that in the latest version it has re-usable velco strips to hold the trip chain to the anchor rather than leaving plastic cable ties at the bottom of the sea.
Sustainable Sailing 