I'm taking a part in developing some application which will run on a virtualized platform, currently it's going to be on VMware ESXi but I would not exclude the KVM option.
The application is real-time and going to be very sensitive to resource shortage, especially to CPU and network bandwidth. Because of this extreme sensitivity we need some health monitoring mechanism that will be able to gather statistics about the system resources provided to a specific virtual machine with our application running inside. It may have a feature to record collected statistics to a log file or send alarms. It’s not a problem to collect such data from the host (hypervisor) level, but the application running inside the VM hasn’t got the required permissions, so cannot access ESXi API as well.