The most common tools which will help VARs be proactive are PerfMon and SQL Server Profiler. PerfMon can provide baselines which can be used to detect deteriorating performance and send alerts to the management team. SQL Server Profiler, in all but the standard template, will add significant load on your SQL Server, but is very useful for providing a window into the activity of your SQL Server.
There are also several tools which allow for remote RDBMs management, like MyLittleAdmin. However most remote DBAs use tools like Microsoft' Remote Desktop Connection which gives them complete access to the remote desktop, or tools like Terminal Services or Citrix MetaFrame which can host Management Tools (like SQL Server Enterprise Manager, or SQL Server Management Studio) remotely.
This was first published in February 2007