Currently the only way to get one value into host A from host B is with a calculated item type in B that says last(/HOST-A/status). This is not dynamic enough when it gets to host prototype discovery since you won't know what the name will be of host A beforehand. A work around would be to allow user macros in Formulas that say last(/{$HOST}/status) or to allow nested calculations last(/last(//conf.hypervisor)/status).