Disclosed examples involve collecting a cookie at a client device based on media accessed via a web page at the client device, and selecting a portable device identifier at the client device. The portable device identifier corresponds to a closest one of a plurality of portable devices in wireless communication with the client device. The portable device identifier is associated with a particular person. In response to instructions embedded in the media, a hypertext transfer protocol (HTTP) request is sent to a server. The HTTP request includes the cookie, the portable device identifier, and information identifying exposure to the media.