In this case vCenter Server (the primary instance) could be a VM or a physical system. The secondary must be a VM!
Optimize availability and resiliency for VMware vCenter Server in any situation. VMware vCenter Server Heartbeat delivers the maximum uptime for your virtual datacenter infrastructure, ensuring consistent operation, even when VMware vCenter Server is threatened by unplanned or planned downtime.
vCenter Server 4.x has not been qualified with third party clustering products such as Microsoft Clustering Service and Veritas Cluster Services. VMware does not support third party clustering products.
Is it a good choice-using FT for virtual vCenter server redundancy?
Not yet... vCenter Server 4.0 require 2 vCPU (expecially if you have also a local DB).
VMware FT actually can work only with VM single vCPU. So or you keep an unsupported vCenter Server (because for a small environment vCenter Server may "work" also with a single vCPU), or you cannot use VMware FT.