Described is a technology by which a communications identifier such as a telephone number is used in selecting relevant content (e.g., an advertisement) for outputting as audible and/or visible information to a destination device. The communications identifier is used like a search term/keyword to determine content relevant to that identifier. A telephone number may be the identifier, selected based on a partially-dialed or actually dialed number, or a user's current scrolling position among listed telephone numbers. A telephone number of an incoming call may be used as the identifier. Profile data and/or state data may be used in selecting relevant content. Some of the profile data may be mined based on previous user activities. In one example, the content may be provided via a remote source of the content, and used immediately or cached for later use (e.g., output).