Re: But how do you make a phone call with it?
Sony make a little Bluetooth device about the size of a little finger. It has a small monochrome display, a 3.5 mm headset socket and physical call and media transport buttons. it can also be used as a standalone Bluetooth headset. As a bonus, it contains a standalone FM receiver, and has a clip for attaching to shirt pockets etc
It could be a good companion to this Gemini device.