Satellite SMS check-in on iPhone
How to prepare your iPhone for satellite check-in before heading off-grid — save the service number, verify your setup, and understand what to do on trail.
When you are in a dead zone with no cellular or Wi-Fi signal, the satellite SMS check-in lets you check in and reset your safety timer by sending a short pre-filled text message from your iPhone's native Messages app. No separate satellite device needed — it uses Apple Messages via Satellite, built into iPhone 14 and later.
This guide covers everything you need to do before your trip to make sure it works when you need it.
Do this setup at home, not at the trailhead. You need a cellular or Wi-Fi connection for most of these steps.
Requirements
- iPhone 14 or later (all models — not SE 3rd generation)
- iOS 18 or later
- An active SIM card (removing or disabling the SIM removes satellite access)
- iMessage enabled
Apple Messages via Satellite is available in the United States, Canada, Mexico, and Japan. Outside these regions, you can still use the satellite SMS check-in over cellular if you have signal — the message format is the same.
Confirm your iPhone and iOS version
Go to Settings → General → About and check:
- Model name: iPhone 14 or later (any variant). iPhone SE 3rd generation is not supported.
- iOS version: 18.0 or later.
If you are on an older iOS version, go to Settings → General → Software Update and update before your trip.
Screenshot coming soon
Settings → General → About
iPhone About screen showing model name (e.g. iPhone 15 Pro) and iOS version (18.x)
Enable iMessage
Apple requires iMessage to be turned on before you go off-grid for satellite messaging to work.
Go to Settings → Apps → Messages and confirm iMessage is toggled on.
Screenshot coming soon
Messages settings — iMessage toggle on
Settings > Apps > Messages screen with iMessage toggle highlighted and switched on
iMessage only needs to be enabled — you do not need to send a message to anyone before your trip. Just confirm the toggle is on while you still have a connection.
Save Trailkeep's service number
When Trailkeep opens your Messages app with the pre-filled check-in, the To: field populates reliably when the number is already saved in your Contacts. Without it, the field may be blank and you would need to type it manually.
Save this number in your iPhone Contacts:
+1 844 743 3008 — save it as "Trailkeep Check-in" or similar so it is easy to recognise.
Screenshot coming soon
Contacts — Trailkeep service number saved
iPhone Contacts card showing the name 'Trailkeep Check-in' and phone number +1 844 743 3008
If the To: field is blank when Messages opens, type the number manually — +1 844 743 3008. The message body is already pre-filled, so you only need to add the recipient and tap send.
Run the satellite connection demo (recommended)
Apple provides a built-in demo that simulates the satellite connection flow — no signal required, no message is actually sent. Running it once before your trip means the real flow will feel familiar when you are cold, tired, and off-grid.
Go to Settings → Apps → Messages → Satellite Connection Demo and walk through it.
Screenshot coming soon
Messages settings — Satellite Connection Demo
Settings > Apps > Messages screen with 'Satellite Connection Demo' row highlighted near the bottom
The demo shows you how to hold your phone and find a satellite lock. In ideal conditions (clear sky, no heavy canopy) a real message takes 30 seconds to send. Under moderate foliage it can take over a minute.
How it works on trail
The satellite SMS link is always visible below the Check in button on any active, uncompleted day — in both the Home tab and the Trip Planner. You do not need to be offline to use it, but it is designed for when you have no data connection.
Screenshot coming soon
Home tab — satellite SMS link below Check in now
Active trip card on the Home tab showing the primary 'Check in now' button and the quiet 'No signal? Check-in via satellite SMS' link below it
Screenshot coming soon
Trip Planner — satellite SMS link on a day row
A day row in the Trip Planner showing the Check-in button and the satellite SMS link below it
The flow
- Tap the satellite SMS link — the app captures your GPS coordinates for up to 2 seconds, then opens Messages.
- Messages opens with a pre-filled message body:
OK TK-[token]orOK TK-[token] lat,lonif GPS was available. - Confirm the recipient is set to +1 844 743 3008. If the To: field is blank, type it in.
- Tap send. iPhone handles the satellite connection — point yourself toward clear sky if needed and follow the on-screen direction arrows.
- Switch back to Trailkeep. The app detects your return automatically and confirms the check-in. If it does not, tap "I sent it" in the dialog manually. Either way, the app extends your check-in deadline by 36 hours immediately so the overdue banner does not fire while the message is in transit.
- Server confirmation — when Trailkeep's server receives the SMS, your day is marked complete and the timer resets with the real value.
Screenshot coming soon
Satellite check-in dialog — launched state
The Trailkeep satellite check-in dialog in its 'launched' phase, showing the instruction text and 'I sent it' / Cancel buttons
After sending
A compact "Check-in sent · Send again" badge replaces the link while the server confirms. It clears automatically once confirmation arrives when you regain connection.
Screenshot coming soon
Satellite check-in — sent badge
The 'Check-in sent · Send again' inline badge shown below the day row after the satellite SMS was initiated
If confirmation does not arrive
The badge stays until the server confirms. This is normal — you may be offline for hours. Once you regain any data connection (cellular, Wi-Fi, or even a brief signal window), the app reconnects and clears the badge automatically.
If the badge is still showing after you have had a reliable connection for several minutes:
- Tap "Send again" — the app resets and walks you through the flow again
- Check the Messages app — confirm the message shows as delivered (not failed). If it failed, move to an open area with a clear view of sky and retry
- Use the normal Check in button if you now have data — both paths are safe to use, they will not double-count
For further help: Safety timer troubleshooting
Before you leave: checklist
- iPhone 14 or later, iOS 18 or later confirmed
- iMessage enabled
- +1 844 743 3008 saved in Contacts as "Trailkeep Check-in"
- Satellite Connection Demo completed at least once
- Emergency contacts added in Trailkeep (Account settings → Emergency tab)
- Trip has a start date and end date set
Related
Set up your safety network
A step-by-step guide to adding emergency contacts, configuring your safety timer, and verifying the QR flow before your trip.
Satellite SMS check-in on Android
How to prepare your Android phone for satellite check-in before heading off-grid — set Google Messages as default, save the service number, and verify your carrier supports satellite SMS.