But Unifi should be able to implement this with zero extra hardware, just with VPN-style clients on phones and laptops? I'm just surprised this needs an extra

But Unifi should be able to implement this with zero extra hardware, just with VPN-style clients on phones and laptops? I'm just surprised this needs an extra device. It would make sense if the device provided its own connectivity (with global wireless service, say), but this doesn't seem to be the case here. It still needs an uplink.