You actually have a few options:
VMware VIX 1.6.2 and vmrun (installed on an Admin Window/Linux box) to shutdown the guestOS if you have VMware tools installed on the VM
*Use the traditional CLI tool vmware-cmd on the ESX host itself
*RCLI for either Windows or Linux
*VI Perl Toolkit
*Powershell
Majority of these can be scripted and automated through some type of scheduled tasks depending on the executing host type (WIN/NIX)
You can find some more info at: http://engineering.ucsb.edu/~duonglt/vmware/
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--William
VMware ESX/ESXi scripts and resources at: