I'm not sure, that's why I removed my post. I know that you need to pay for access to the postcode database but I'm not sure whether there's any agreement to let emergency services have free access.
You don't always have a data connection to send that via an app. I suppose you could make an app to send a text message with that info, but that's not always reliable in low signal areas. At least if you can easily tell someone the info over the phone you'll know for sure they received the info.
If you have no data or SMS then it is extremely unliekly you have any voice.