I recently found basicstate.com. BasicState is a great (especially since it is free) web site uptime and performance monitoring service.  The service doesn’t have a lot of bells and whistles.  It just provides a single service very well.   BasicStats can send email or text alerts when DNS or a web site is unavailable.  The service maintains a history and can email a daily report or show trends in graph format.  The history is great for explaining actual downtime to clients.   

 

Average Response Times for aaronkjackson.com