Abstract: A method for a positioning server configured to locate positioning devices and to maintain information on users, who are associated with respective positioning devices. The server receives one or more alert messages from an alerting positioning device. Each alert message conveys identifying information of the alerting positioning device. The server uses the identifying information to retrieve a location estimate of the alerting positioning device. The server forms a first set of other positioning devices in a vicinity of the alerting positioning device and sends an assist request message to the positioning devices in the first set. The assist request message indicates the location estimate of the alerting positioning device and/or said descriptive information.

Abstract: A mobile data processing device configured to assist in locating a user. The device comprises an enclosure and an attachment base for attaching the device to a garment, lanyard or strap wearable by a user. The attachment base moves between a first (“normal”) position and a second (“alert”) position with respect to the enclosure in response to an external force acting on the enclosure. The device further comprises a detector system for detecting removal of the attachment base from the normal position, and an alert signal generator configured to send an alert signal in response to said detection. The alert signal can be generated quickly by grabbing the enclosure and pulling the device downwards.

Abstract: A method for a positioning server configured to locate positioning devices and to maintain information on users, who are associated with respective positioning devices. The server receives one or more alert messages from an alerting positioning device. Each alert message conveys identifying information of the alerting positioning device. The server uses the identifying information to retrieve a location estimate of the alerting positioning device. The server forms a first set of other positioning devices in a vicinity of the alerting positioning device and sends an assist request message to the positioning devices in the first set. The assist request message indicates the location estimate of the alerting positioning device and/or said descriptive information.

Abstract: A mobile data processing device configured to assist in locating a user. The device comprises an enclosure and an attachment base for attaching the device to a garment, lanyard or strap wearable by a user. The attachment base moves between a first (“normal”) position and a second (“alert”) position with respect to the enclosure in response to an external force acting on the enclosure. The device further comprises a detector system for detecting removal of the attachment base from the normal position, and an alert signal generator configured to send an alert signal in response to said detection. The alert signal can be generated quickly by grabbing the enclosure and pulling the device downwards.

Abstract: A method for a positioning server configured to locate positioning devices and to maintain information on users, who are associated with respective positioning devices. The server receives one or more alert messages from an alerting positioning device. Each alert message conveys identifying information of the alerting positioning device. The server uses the identifying information to retrieve a location estimate of the alerting positioning device. The server forms a first set of other positioning devices in a vicinity of the alerting positioning device and sends an assist request message to the positioning devices in the first set. The assist request message indicates the location estimate of the alerting positioning device and/or said descriptive information.