From W3C Wiki
Abigail always wears a gaudy glass-emerald brooch. It's not that she particularly likes the look of the brooch, just that it's also a panic button. Abigail's a bit of a hyperchondriac and her husband has a history of heart trouble. The emerald is backed by a piezo crystal and squeezing the brooch changes a flag in it's WiFi http client. This calls a Semantic Web Service to which she is subscribed. The service picks up Abigail's location with the help of local WiFi receivers and looks up her personal record. The nearest emergency services are contacted and given her location together with the URI of her family's medical records. So far all this is standard off-the-shelf web service functionality. At this point the Semantic Web comes into play starting by picking out the (semi-public) parts of the medical details, considering likely problems and deriving appropriate first aid actions. People she knows (contained in her FOAF profile) have their schedules checked to see if they're in the area and available. They, together with any known medics in the area have the appropriate information delivered to their mobile devices and are bleeped. At the same time her insurance company's account is debited by the appropriate amount and part of the funds made available for collection by anyone that goes to Abigail's aid.