Looks like tonari[0] will have some heavy competition sooner than expected. This seems to have a lot more attention paid to the sensation of depth than the tonari offering. Could see this being popular at high end senior care facilities.
At Atlassian, they built a Portal inspired portal that connects the Sydney and SF office during one hackathon. Basically a camera behind a 2way mirror (and decorated with blue/orange LEDs in an oval frame). Tonari looks a lot more like that than Starline.
[0]https://tonari.no