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If you’re lost on a mountain in thick fog or a blizzard, even a mobile phone isn’t much help if you can’t describe where you are. Jim and Janice Glover of Kilmarnock in Scotland have the answer (GB 2362978). Everyone in the walking or climbing party carries a GPS satellite navigation locator, combined with a radio transceiver. Each device continually checks its own position and automatically transmits it to all the other devices in the group, allowing each one to display the position of the others on a map. Anyone who is lost just sends out a “Help” signal to all the other devices. If someone is injured and falls silent, they can still be found because everyone else knows where they are. The system could also be useful, its inventors say, to keep families in touch during outings at theme parks and the like.