It seems that a lot of my competitors seem to be selling the fact that they are using monitoring software that will notify them by email or SMS if one of their clients servers has a problem or if connectivity to the Internet is lost. I realise that this will require software running on the servers that maintains a heartbeat to an external company that can then notify myself. I am looking for recommendations from Experts for products that fullfill my needs. Ideally it would be open source with my own location being the point that is kept in constant contact with my customers servers. It should notify me if exchange goes offline or if the server is going to be out of disk space. High processor usage or memory usage etc My customers are typically SMEs with often one SBS 2003 or 2008 Server.