Yes, we all have skype on our machines and I show them how to dial my phone extension if they need anything.
Edit: also for clarification, we discuss the problem ahead of time to make sure they understand it and ask any questions. For my group it's always a basic full stack problem. Here's a mockup and a basic install of visual studio and MSSQL, show me you can CRUD some data and present a decent UI. then we'll talk about how you did it.
Do you let your interviewees reach out (possibly via IM) to your interviewers with specific questions?