Satellite messengers and satellite SOS on phones

The device determines its position via satellite navigation (GNSS), like a satnav. It sends messages and position data to communication satellites of a commercial network, which relay them to ground stations. From there, ordinary text messages go to your contacts and SOS alerts go to the provider's emergency response centre, which alerts the responsible rescue services in that country.

Because the satellite link carries only a little data and needs a clear view of the sky, it can take minutes for a message to get through. Dense trees, rock walls, tent roofs or your own body can weaken the signal. It is best to place the device in an open spot with as much open sky as possible.

The big difference from a PLB: a messenger usually allows two-way communication. The response centre can ask questions and you can describe details – which helps rescuers send the right help. In exchange, it depends on a subscription, a commercial network and a charged battery.

A satellite messenger is only as good as its preparation. Activate the service in good time before the trip and check that the subscription is still running – without an active service, the SOS function may not work. Store emergency contacts and important medical notes, and create preset messages such as 'All fine, we are at camp'.

Before the trip, send a test message under open sky – explicitly not an SOS – and have its receipt confirmed. That way you know the device, service and contacts work, and you practise using it. Fully charge the battery and take a power bank if possible.

Agree with your contact person when you will check in and what they should do if messages do not arrive. A missing check-in can have many harmless causes – poor sky view, a flat battery. That is why it is important to settle beforehand how long they should wait before calling for help.

Trigger SOS only in genuine distress. If you have mobile signal, calling the local emergency number (112 in the EU) is usually faster and more direct. After triggering it, leave the device on, place it with a clear view of the sky and answer the response centre's questions: type of emergency, number of people, injuries, hazards.

Save battery by writing only what is necessary and switching off unneeded functions. Stay in one place if possible. Also use visual and sound signals so rescuers can find you on the spot. If SOS is triggered by mistake, cancel it as instructed and tell the response centre at once that it was a false alarm.

Some newer smartphones can send emergency messages via satellite without mobile coverage in certain countries. Availability, countries and operation vary greatly and change over time. Before travelling, check whether your phone can do it and whether the service is offered in your destination country. If there is a demo function, try it out – in a real emergency there is no time to learn how it works.

A satellite phone allows real voice calls but is more expensive and heavier. Some countries restrict importing or using one – check local rules before you take one along. For all satellite devices: they need a clear view of the sky and power.

A satellite messenger is especially useful on trips in areas without reliable mobile coverage: remote mountains, deserts, waterways or sparsely populated regions. Beyond emergencies, it also helps day to day on the trip, for example to send relatives regular check-ins – which can prevent needless worry and searches.

As your only emergency device, it is only as reliable as its battery and subscription. In narrow gorges, dense forest or indoors it can fail. This entry does not assess individual devices or providers; coverage and services change. What matters is that you know your device, that it is charged and activated, and that your contact person is in the loop.