I've had several chats and two phone calls from Belkin on this issue. To cut a long story short, what they want me to to is to have WiDi software installed in PC. Yes, I understand that WiDi software doesn't work with Win 8.1, and that was what I told them too, but they said it was how their product was meant to work. And they directed me to Screencast user manual to support their claim.
So, who is gonna move first: Intel to update the drivers / software, or Microsoft who spoiled working thing? I really don't expect Belkin to accept back all the Screencast units, to flash the firmware, this really does not look like their fault. Really, why Intel wouldn't make WiDi software compatible with Windows 8.1? You can not just say that WiDi works now from charms bar, since it obviously doesn't, or at least it doesn't work well.