Barnevernet is a program for, eh, remote management of Windows machines. Think of it like TeamViewer, but without Big Brother and without $500 license (and with much less features).
Access someone's Windows desktop by just dropping a small (14 kB) .exe.
Q: Why don't you just use VNC server/Meterpreter/PuTTy/…?
A: I found none with installation I can guide over the phone. And these people are behind NAT/firewall with no incoming connections.