The idea of digital assistant does not require it to be tied to any specific device. It can live in the cloud and follow you anywhere the entrypoint being any device you are using (and you are logged on). Think of Jarvis from the Iron man movies. If I understood the aim of the VIV correctly, they are trying to do this by not tying the service to any given platform but being this platform. This is what makes it so powerful and intriguing (and scary if you do not have the control of the assistant).