A digital assistant (“Ann”) interacts with the owner's mobile device. He sees a product on a third party website. If she sells it cheaper, he buys from her. Ann gets more business. A non-owner near Ann cannot buy directly from her. He says he wants to buy on his device. Ann says an URL. His device decodes and shows the page from Ann. He buys from it. Ann gets more business. A user near Ann asks to analyse a news page on his device. She advises if the page is real or “fake news”. Two users with mobile devices near Ann use her to play a game, on website or app. A user uses a Virtual Reality device near Ann. He interacts with her via voice. She advises on what he sees and can do in the VR. Two digital assistants from different firms are near each other and a person with a mobile device. An assistant benchmarks itself against the other by passive and active means. Ann can have a barcode, that lets users pass information between her and their devices.