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 Check-in 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.
Outside the US, standard international SMS rates from your carrier may apply when sending the check-in message.
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:
+1 833 676 0717 — 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 +1 833 676 0717
If the To: field is blank when Messages opens, type the number manually — +1 833 676 0717. 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 Check in by text link is always visible below Check in now on the Start tab for the current uncompleted day. You do not need to be offline to use it, but it is designed for when you have no data connection.
Screenshot coming soon
Start tab — Check in by text below Check in now
Active trip card on the Start tab showing the primary 'Check in now' button and the quiet 'No data? Check in by text (cell or satellite)' link below it
The flow
- Tap Check in by text — 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 +1 833 676 0717. 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. On the Daily progress timeline, today's row asks Did your check-in text send? Tap Yes, it sent only if the message left Messages. The Check-in Timer extends locally by your configured window (24h or 36h) only after you confirm, so the overdue banner does not fire while the message is in transit.
- Server confirmation — Trailkeep processes the SMS on the server (day complete, timer reset). You do not need to wait for a reply text from Trailkeep — Messages shows whether your text sent or failed. After Yes, it sent, you can keep hiking; the in-app pending row clears when you regain data. A confirmation text back from Trailkeep is planned for a future update.
Screenshot coming soon
Text check-in — confirm on daily progress row
The current day row on the Start tab timeline showing the amber confirm panel 'Did your check-in text send?' with Yes, it sent and No, I'll retry buttons
After you confirm
The day you sent from shows Text sent · pending on device with Reset. The next day becomes current — Check in now and No data? Check in by text target that day. Everything clears automatically on the sent day once server confirmation arrives when you regain connection.
Screenshot coming soon
Text check-in — virtual done row
A completed daily-progress row showing meta 'Text sent · pending on device' and a Reset link, with the next day highlighted as current
If the app still shows pending
This is about the in-app Text sent · pending on device row — not a reply SMS from Trailkeep (that is not sent yet). The meta stays until Trailkeep confirms on the server and the app syncs. You may be offline for hours — you do not need to wait on trail for the row to clear. Once you regain any data connection, the app reconnects and clears the row automatically.
If the meta is still showing after you have had a reliable connection for several minutes:
- Tap Reset on that row to clear the pending state on your phone and start the text flow over
- 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
- +1 833 676 0717 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 the Check-in 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.