I was just checking something and I saw that HVRemote was updated a few days ago (to v1.08) include support for Windows Server 2012 R2, Hyper-V Server 2012 R2, and Windows 8.1 Client Hyper-V.
HVRemote is a Codeplex (not supported by Microsoft) product that makes enabling remote support of workgroup machines a lot easier. It is written by John Howard of Microsoft who works in the Hyper-V team.