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Worked Example: Two Phones Together

Summary​

Two phones working together — a dedicated monitoring phone that detects departures via Bluetooth, and your daily phone that receives the alerts — is a supported way to deploy Sentinel Circle, not just an illustration. It is what the Email and Notification sensors were built for, and the reason their subject filters default to the words AWAY and HOME: those defaults are the two halves of this pattern, and they stay in English in every language so the two phones agree whatever each one is set to.

Details​

The setup​

Phone A: Monitoring Phone (dedicated, always at home)

  • An older phone (even 10+ years old) placed at the exit.
  • Runs Sentinel Circle with a Bluetooth sensor watching a beacon the person carries.
  • When the beacon goes out of range, sends an email to your inbox.
  • When the beacon returns, sends a recovery email.
  • Always plugged into a charger.

Phone B: Your Daily Phone (caregiver's phone)

  • Your everyday phone, carried with you.
  • Runs Sentinel Circle with an Email or Notification sensor watching your inbox.
  • When a Sentinel Circle email arrives, shows an Alert Screen dialog.
  • Works in the background with no special configuration needed.

Phone A configuration (Monitoring Phone)​

Sensor:

  • Add a Bluetooth sensor and select the beacon the person carries.
  • Use the default alert delay (90 seconds from leaving to alert).

Channel:

  • Add an Email channel with your email provider's outgoing server settings.
  • Set the recipient to your own email address.
  • Set the monitor's Unsafe Message to include "AWAY" (e.g., "AWAY - Person has left") — this becomes the email subject that Phone B will detect.
  • Set the monitor's Safe Message to include "HOME" (e.g., "HOME - Person has returned") — Phone B detects this in the email subject.

Monitor:

  • Create a monitor linking the Bluetooth sensor to the Email channel.
  • Turn on "Send an alert when this monitor becomes safe again" so you also get a "person returned" email.

Phone A optimization (kiosk mode) — since this phone is dedicated to monitoring and always plugged in:

  1. Turn off battery optimization for Sentinel Circle.
  2. Turn off any brand-specific power savers (Samsung, Xiaomi, etc.).
  3. Turn on "Keep Screen On" in Sentinel Circle Application Settings.
  4. Set screen brightness to minimum.
  5. Set volume to minimum and enable silent/vibrate mode.
  6. Lock the app (tap lock icon > set password).
  7. Place the phone near the exit door, plugged into a charger.

Phone B configuration (Your Daily Phone)​

Sensor — Option 1: Email Sensor (recommended)

  • Add an Email sensor with your inbox's server settings.
  • Set Unsafe Subject Filter to match the leaving email's subject (default: "AWAY").
  • Set Safe Subject Filter to match the recovery email's subject (default: "HOME").
  • Set how often it checks (e.g., every 30 seconds).

Sensor — Option 2: Notification Sensor (alternative)

  • Add a Notification sensor watching Gmail.
  • Set the same Unsafe/Safe filters as above.
  • Requires Notification Access permission.
  • Reacts the instant the email notification appears — no waiting for the next check.

Channel:

  • Add an Alert Screen channel to show a full-screen dialog when triggered.
  • Optionally add a Sound channel for an audible alarm.

Monitor:

  • Create a monitor linking the Email/Notification sensor to the Alert Screen channel.
  • Turn on "Send an alert when this monitor becomes safe again" to also see when the person returns.

Phone B: no special setup needed. Your daily phone can run Sentinel Circle in the background with no special power or battery changes needed. Whichever sensor you chose checks for the email or notification, and the Alert Screen appears even when the phone is locked.

How it all works together​

Person leaves home with beacon:

  1. Phone A: the beacon goes out of range.
  2. Phone A: double-checks it's really gone (about 90 seconds).
  3. Phone A: sends the "AWAY" email.
  4. Phone B: its sensor spots the email.
  5. Phone B: the Alert Screen pops up on your phone.

Person returns home:

  1. Phone A: the beacon is back in range, and it's confirmed.
  2. Phone A: sends the "HOME" recovery email.
  3. Phone B: spots the recovery email and alerts you that they're back.

Example: Sentinel Circle Mode versus Sentinel Gate Mode​

Wi-Fi and Bluetooth sensors can work in two different directions, depending on what you're watching for:

Sentinel Circle Mode (default) — use this when the device should normally be there. The alert fires when it leaves and can no longer be found. Use cases:

  • Monitoring a person at home — the beacon they carry leaves the phone's range (Trigger: when absent, Debouncing: recommended).
  • Monitoring a specific place like a workplace or daycare — alert when the person leaves (Trigger: when absent, Debouncing: recommended).
  • Monitoring a family member's own device — alert when it goes out of range (Trigger: when absent, Debouncing: recommended).

Sentinel Gate Mode (Trigger When Detected) — use this when the device should normally NOT be there. The alert fires the instant it's detected entering. Use cases:

  • Watching a property entrance — a Bluetooth scanner by the gate detects when someone carrying a phone or tracker walks in (Trigger: when detected, Debouncing: no).
  • Watching for vehicle arrivals — detects a car's built-in Bluetooth, or a tracker on the keys, entering the driveway (Trigger: when detected, Debouncing: no).
  • Watching visitor access — a Wi-Fi or Bluetooth sensor at an entry point detects an unrecognized device connecting (Trigger: when detected, Debouncing: no).
  • Watching for unwanted intrusions — alerts when a specific person's tracked device enters a restricted area (Trigger: when detected, Debouncing: no).
  • Watching for vehicle departure — detects a car's built-in Bluetooth being started or taken without permission (Trigger: when detected, Debouncing: no).