We have considered allowing users to define a scope of interest which we could monitor and report on. Imagine you'd like to know who in your tree has been updated recently, or who has multiple parents, or who has sources, etc., etc. You could define a scope of interest for example assume I'm working on my Brewster line. I go over to Sarah Augusta Brewster and tell the system I want to define a scope of interest starting at Sarah and going back 5 generations and down 2 generations at each generation. The system would then report to me about activity in this portion of the tree.
We took this concept a step further and hooked it up to a technology called RSS which basically allowed us to run a report against a scope of interest and pipe it out using RSS to any number of news readers. Here's a snapshot of the feed from my tree in Google Reader.
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You can click on any of the items and it takes you to the person in the tree. I shared this list with my sister, who is an avid genealogist, and she immediately began using it as a punch list of things to do on our tree. I then got new things on my list indicating that people in the tree had been updated. You can imagine how useful this would be to keep tabs on people in the tree and see who is updating them. Before you get too excited about this, remember, this was just a quick demo we hacked together to show the concept. It is not ready for prime time.