I feel like this reflects the movie Her (2013). This solves the input problem better than speaking out in public, especially on a crowded train.

I do think seeing an email on a smartglasses lens is better than hearing it read to you. So I can see this as just an input device, but the outputs don't have to be sound back to you.

I'm guessing they are situating themselves to be bought or at least licensed out to the big smartglasses players.