Techniques for communicating with a user on a network include receiving acceleration data that indicates acceleration of a mobile network node associated with a user of a network. A communication state for the user is determined based at least in part on the acceleration data. The communication state indicates a type of network communication suitable for communicating with the user. Network communications with the user are based on the communication state. Among other uses, such techniques allow a network communicating with a human through a mobile node carried by the human to infer from stopped or unusual motions when the human's ability to receive or act on communications is impaired or otherwise affected.