VirusScan for Offline images is available, which uses VMSafe APIs to scan offline disks accssed via ESX
Nothing is currently roadmapped for on-access scanning - no AV vendor has this technology available (or even roadmapped as far as I'm aware) yet.
Watch this space I guess
We announced something called MOVE (McAfee Optimized for Virtual Environments) at Citrix's Synergy event a couple months ago. MOVE is a platform that is similar to the VMSafe apis. However, MOVE supports VMWare, Citrix, and Microsoft. We will be shipping in next month or two both MOVE (the platform) and MOVE AV (the first product on that platform.) MOVE AV offloads the AV scanning from the guest VMs into the hypervisor. We will be launching this in more detail at our Focus customer event in early October.
MOVE AV uses it's own mechanism. This mechanism is part of the MOVE platform itself. Shoot me an email at email@example.com if you want more details. I can get the PM in touch.