It's disappointing that 6 years later there's still no solution. The window has passed for my kids - but it would have been really nice to be able to have large format TV based video calls with the grandparents. I tried to set something up with a laptop, but it was always too janky and fiddly to work well.
I'll put this in the bucket with all the other weird human-facing hardware that didn't work out in the market, like the Spotify Car Thing[1], Amazon Dash[2], Motorola Atrix[3], and the Corel/Rebel.com Netwinder[4].
But it's pretty cool that someone is making an effort from On-High to get adb working on these Portal devices. It's not as great as it could be, but it beats a kick in the pants.
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[1]: A cute dashtop widget that provided physical controls and a screen for Spotify and...apparently nothing else
[2]: A button! That orders one thing, only, from Amazon! Push button, receive thing! (I actually bought one of these on the first Prime Day for almost nothing. I never set it up or bothered hacking it; it got deliberately binned during the last move.)
[3]: Just plug your phone into this screen-widget, and you won't need a laptop! Pinky-swear! (And we'll have Verizon finance it for you!)
[4]: Let's sell a very low-end all-in-one tabletop ARM PC in retail stores at a direct loss, and profit from offering dial-up internet! (What could go wrong!)