Hi,
Not sure if i'm clear with your query
"I did not mean the EVC feature, but the new 5.1 feature to move VMs across not shared datastores and hosts without any downtime.
Is this feature implemented in vCenter or is it Host related?"
Thumb Rule:VC should be always equal to or higher than esx/esxi version 
To make use of Migration feature without a shared storage we need both ESX and VC in 5.1 version.