This is more than anything a suggestion for a customization to the Summary Widget. It would be really great if you could select the area (of points for instance) that you want to summarize - rather than the widget summarizing everything within the extent. Any ideas on how to achieve this?
One option is to use the Incident Analysis widget and only configure the Summary option (without Weather, Proximity or Closest Feature). This will allow the user to draw a point, line, polygon and get similar summary information. Does it work for you?