The Pocket Naturalist is a conceptual design. There are two forms it could take: the high-tech and the low-tech.
In the high-tech version, users would take a snapshot of the plant with their cameraphone, and the Pocket Naturalist program would upload the image to a server, where pattern-recognition software would compare the characteristics of the plant to a large database of images. The user would then be told the kind of plant, and charged a fee for the use of the service.
In the low-tech version, the Pocket Naturalist would be a taxonomy key, asking the user questions to achieve identification. It could be text-only or include images. Existing paper-based taxonomy keys usually identify any plant in their repertoire within 5 - 10 questions.
For either implementation, the Pocket Naturalist could be an application or a mobile-accessible website.
Besides satisfying idle curiosity, this could be a valuable tool to improve our relationship with our local surroundings, by increasing our understanding of it. In addition to the tool giving you the name of the plant, it could also provide other information, such as where the plant is native to, whether it is edible, or unique aspects of its biology.
The Pocket Naturalist could be a gateway for adults and children to get more involved with their local flora, and to increase their environmental awareness.