Siflo: Outdoor Communication
Mesh messaging, signals & SOS
Free · Designed for iPhone. Not verified for macOS.
Signals, messages, photos and SOS hop from phone to phone, with or without a network, and now from your Apple Watch. No account, end-to-end encrypted.
Canyoning, climbing, caving, mountaineering, kayaking, expeditions: when there is no network, the waterfall roars or a ridge hides your partner, Siflo keeps your group in touch. Signals, messages, photos, voice and SOS hop from phone to phone, with or without a network.
WORKS OFFLINE
• Messages hop from phone to phone over Bluetooth, from one end of the group to the other.
• If one member has 4G, the whole group benefits: internet relays link distant sub-groups, and take over from each other if one stops answering.
• Messages are kept and handed over to latecomers.
• Range test mode: see which phones you reach, over which link (Bluetooth, LoRa, through another phone, internet) and how far, and record the session to prepare a canyon or cave outing.
ONE TAP, EVERYONE KNOWS
• STOP, OK, Give rope, Pull up the rope: the whistle codes as big buttons, usable with gloves or a wet screen.
• Each signal arrives with the name of who sent it, as vibrations, whistle blasts and an alert, even on the lock screen.
• You see who received it, who saw it, and who has not yet.
ON YOUR WATCH
• Apple Watch: hold the center of the screen, slide to a signal and let go to send it; dictate a message, record a voice message or start an SOS without taking out your iPhone.
• Signals you receive buzz on your wrist. The watch works through your iPhone: it holds no key and sends nothing when the iPhone is out of reach.
EVERYTHING TO COMMUNICATE ON AN OUTING
• Text messages, photos and short voice messages to the group or to one person; reactions, edits and deletions.
• Group topo: the pages and PDFs of the route description, kept on every member's phone and readable without network.
• Before you go: a checklist per activity, and an offline safety sheet to call for help and signal to rescuers.
• SOS with your position, relayed to every Siflo user in range, that keeps ringing with the screen off; also by SMS to the numbers your group chose.
• Your own signals for any activity, and your position shared only when you decide.
PRIVATE BY DESIGN
• No account, no phone number, no ads.
• End-to-end encryption: not even our relay servers can read your messages.
• The protocol is checked with formal proof tools and tested against malformed or crafted messages.
• Your position is never shared without your explicit consent.
• Strangers in range only see a public name; your nickname stays for your groups and contacts.
Siflo is free and will stay free. If it helps your outings, you can leave a tip from the settings.
Siflo adds to your whistle and radio; it does not replace them. Radio does not go through rock.
Ratings & Reviews
- This app hasn’t received enough ratings or reviews to display an overview.
Offline map of the area: an editor chooses a square of 10, 20 or 30 km around the outing and adds it to the group's topo; every member downloads it with one tap, or receives it from a member nearby without internet. Trails, contour lines and the group's places stay readable with no network. From the new map icon on the home screen, download areas of your own, up to 50 km: tiles already on your phone are never downloaded again.
Join approval: an admin can ask newcomers to request access through the group's link, and accepts or declines each request.
App lock: fingerprint, face or the phone's code to open Siflo; signals and SOS keep working. A storage manager in Settings shows and frees the space photos, voice messages, documents and maps take.
Watches: the SOS countdown names the group it goes to.
Photos: the caption is the text you were typing.
The developer, Guardia SAS, indicated that the app’s privacy practices may include handling of data as described below. For more information, see the developer’s privacy policy .
Data Not Linked to You
The following data may be collected but it is not linked to your identity:
- Identifiers
Accessibility
The developer has not yet indicated which accessibility features this app supports. Learn More
Information
- Seller
- GUARDIA
- Size
- 34.8 MB
- Category
- Social Networking
- Compatibility
Requires iOS 17.0 or later.
- iPhone
Requires iOS 17.0 or later. - Mac
Requires macOS 14.0 or later and a Mac with Apple M1 chip or later. - Apple Watch
Requires watchOS 10.0 or later.
- iPhone
- Location
- This app may use your location even when it isn’t open, which can decrease device battery life.
- Languages
English and 5 more
- English, French, German, Italian, Portuguese, Spanish
- Age Rating
13+
- 13+
- Contains
Messaging and Chat
- Copyright
- © 2026 Guardia SAS