Quoting from the Tripwire official announcement:
Tripwire today announced that the company has joined the VMware Technology Alliance Partner Program to further help IT organizations ensure successful operation of their virtual environments. Tripwire Enterprise 7 assures control of all configuration change across VMware instances in order to provide continuous operational, regulatory and security compliance…
Tripwire is a well-known security firm focused on host intrusion detection. With this announcement the company is simply stating that it supports its product inside virtual machines, but since they entered the VMware TAP program we can expect they will work to move Tripwire Enterprise from guest level to host one.
Tripwire is only the last vendor announcing such effort. Most competitors will do the same now that VMware is opening its infrastructure APIs through the Vsafe program to move security controls at hypervisor level.