ManageEngine VM Health Monitor tool will address this monitoring requirement.
BSEditor: The ManageEngine VM Health Monitor tool helps an administrator to monitor important attributes of a VMware Server. This Tool can obtain information from ESX/ESXi and VirtualCenter servers, including ESX/ESXi 3.5x, ESX/ESXi 3.0.x;

*Monitor VMware server
ManageEngine VM Health Monitor helps an administrator to view the following variables of a Virtual Machine server.

*CPU Utilization
Memory Utilization
Disk Read / Write
Network Rx/Tx
CPU utilization is approximately equal to the ratio of the used CPU cycles to that of the available CPU cycles.
available CPU = # of physical CPUs x clock rate
100% represents all CPUs on the host are completely occupied. For example, if a four-CPU host is running two virtual machines with one CPU each, and the usage is 50%, the host is using two CPUs completely.

*Memory Utilization
Percentage of memory currently in use. This is active memory as a percentage of total configured or available memory.

*Disk Read Rate
This parameter provides the average number of KiloBytes read from the disk each second during the collection interval. This parameter is expressed in kiloBytes/sec.

*Disk Write Rate
This parameter provides the average number of KiloBytes written to the disk each second during the collection interval. This parameter is expressed in kiloBytes/sec.

*Network Rx
Average rate at which data was received during the interval. This represents the bandwidth of the network. The rate at which data is received across each physical NIC instance on the host.

*Network Tx
Average rate at which data was transmitted during the interval. This represents the bandwidth of the network. The rate at which data is transmitted across each physical NIC instance on the host.

*Monitor virtual machine
Monitor health reports like VM name, guest OS, VM state, virtual processor, virtual memory and virtual network usage.
The variables which are monitored for each Guest OS/ Virtual Machine are as follows.

and more... you can free download VM Health Monitor 1.0 now.