1. A method for an application policy manager and an agent to implement policy-based application monitoring and remediation in a virtual machine (VM) system, the agent being installed on a guest operating system (OS) of a VM on a host, the method comprising: the application policy manager providing a user interface for defining policies on applications running on VMs, each policy comprising one or more monitoring conditions and one or more remediation for the one or more monitoring conditions; the application policy manager receiving a policy for an application on the VM via the user interface; the application policy manager sending the policy to the agent running on the VM; the agent monitoring the application based on the policy received from the application policy manager, comprising: in response to the agent detecting a start condition, the agent starting monitoring the application and sending a first alert directly to a statistics manager or indirectly to the statistics manager via the application policy manager, wherein the statistics manager starts collecting performance metrics related to the application in response to the first alert; and in response to the agent detecting a stop condition, the agent stopping monitoring the application and sending a second alert directly to the statistics manager or indirectly to the statistics manager via the application policy manager, wherein the statistics manager stops collecting the performance metrics related to the application in response to the second alert; when the agent detects a monitoring condition for the application specified in the policy, the agent: sending an alert identifying the application and the monitoring condition directly to an events and alarms manager or indirectly to the events and alarms manager via the application policy manager, wherein the events and alarms manager records the alert; sending a log generated by the application to an email address, directly to a log analyzer or indirectly to the log analyzer via the application policy manager, wherein the log analyzer analyzes the log to determine a cause of the monitoring condition; and performing a remediation specified in the policy for the monitoring condition.