Stumbled upon this great deal. Unsure if it will work with Dex or a rasperry Pi. Confirmed that this works over Miracast; tested with a Dell Laptop. Should work with other Miracast compatible devices. Retail for this was $600.
This was meant to pair with the Elite X3 phone, but given that Windows Phone is now dead looks like prices are dropping; it's the Motorola Atrix Lapdock story all over again.
Tinkering is likely needed to get this to work with anything, so probably shouldnt buy this unless you feel comfortable about doing that. Posts seem to suggest it's fully USB-C spec compliant which means that it could work as an external display with a USB-C to Displayport connector.
Looks like he has ~260 units, about 180 sold already.
Be cautious of other low reputation / new sellers having this same item for a very low price; people are getting burned. This seller (bluefish-worx) is legit.