Monitoring VMware ESXi hosts with simple checks could use the addition of Ready and CoStop support. The official API would imply the following;

vmware.hv.hw.cpu.ready[<url>,<uuid>]
vmware.hv.hw.cpu.costop[<url>,<uuid>]

At the moment the item keys are not supported.

VM's already have the ready value supported but they could also use the costop value.