Karen Net Monitor 3.6 lets you closely monitor your Internet connection by making periodic checks and tests of websites you indicate, checking response times of each server. It offers you exhaustive and detailed reports on each one of the checks made, letting you configure it to automatically send you an email with the history of all the reports and checks done.
For programmers it´s interesting to know that on the author´s web there is the source code of how it is done (in Visual Basic).