Jane talks to Bob, who can be a stranger. She shows him photos on her mobile device. He wants a copy of a photo. Jane could work for a company that wants to promote its products. Her device has product images. She makes data with a link to the image, and her contact information. The data is in a barcode on her screen. Bob decodes the data. He gets her email address. His device replies with an auto-generated message. Her device gets his electronic address. Her device can send a message, offering a discount or extra features about the product. Another use lets Bob comment in text or speech about Jane's photo. His comment is added to the webpage that shows the photo. Other wireless means are possible. Including “chirp”—an identifier of the data is transmitted as audio. Or using accelerometers and geolocation on both devices. The invention permits the automated transmission of photos and contact information between people, with minimal manual steps. A company can use it to build a database of potential customers interested in their products. Another method lets Jane transmit her email address to Bob, who takes a photo of her and emails it to her.