Karoo Sentinel: An advanced anti-theft and security alarm extension

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HesiOX
  • Edited

Hi everyone,

Sharing Karoo Sentinel, an advanced security and anti-theft extension for the Hammerhead Karoo 2 & 3.

Repo & releases: https://github.com/DAVOE75/KarooSentinel

Why I built it: Two main frustrations when leaving my bike outside a cafe or for a quick bathroom stop:

  • Just locking the Karoo screen isn't enough. If someone grabs the bike, I want to know immediately before they get out of sight, and I want the device to physically deter the thief.
  • I don't want to carry an extra Bluetooth tag or heavy lock for quick stops. The Karoo already has an accelerometer, a GPS, a beeper, and an internet connection — it's the perfect built-in alarm system.

Beyond that, I kept it as native-feeling as possible. Clean UI, dark mode to save battery, zero-latency interactions, and full integration with the Karoo's system services.

What it does:

  • Advanced Inertial Detection: Arms the internal accelerometer. The slightest unauthorized vibration or movement triggers the alarm.
  • Hardware Beeper Siren & Screen Flash: When triggered, the Karoo wakes up over the lock screen, flashing red and blasting high-frequency beep patterns directly through the internal beeper.
  • Live GPS Tracking via Telegram: If the bike moves more than 20 meters (Geofence), it silently tracks the thief, sending you live Google Maps links via a Telegram bot every 30 seconds.
  • Di2 / SRAM AXS Integration: You can map the alarm to your shifter's "Bonus Buttons". Arm and disarm the bike without even taking your gloves off or touching the screen.
  • Anti-Shutdown & Sensor Drop Protection: If a thief tries to hold the power button to turn off the Karoo, or unpairs your Garmin Varia radar, the system intercepts it, sounds the siren, and sends a critical push alert to your phone.
  • Silent Trap Mode & Security PIN: Catch them red-handed with silent phone alerts. Plus, a 4-digit PIN prevents anyone from just tapping "Deactivate" on the screen.
  • i18n: Fully translated into 6 languages (EN, ES, FR, IT, DE, PT).

I would love it if you could test it out on your next coffee stop and give some feedback!

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    Simon Lockwood
    • Edited

    This looks really interesting, thanks for developing it. I had a garmin edge unit many years ago with this and used it frequently. 

    Have you tested impact on battery life? That's not a big worry of mine for most rides, but worth knowing if i'm running low on battery life. To be fair, my coffee stops are normally only 10-20 mins.

    Thanks

    Simon

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    Jakub Klima

    What if the BT connection with my phone is lost (eg. the bike is too far from the phone)?

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    Simon Lockwood

    @Jakub - hopelly you would be near enough to hear the beeping noise - or it might encourage the thief to leave the bike and run.

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    HesiOX

    Thanks a lot for the feedback and interest, Simon and Jakub!

    To address your questions:

    1. Purpose & Deterrence (Real-world expectations):
    First and foremost, Karoo Sentinel is designed as a theft deterrent, specifically tailored for quick stops (coffee breaks, refilling water, quick café runs). As with any alarm or even physical locks, a determined thief with tools can take a bike given enough time. Sentinel’s goal is to create immediate friction: an unexpected loud alert that startles anyone touching your bike, draws instant attention from people around, and gives you crucial seconds to react.

    2. Battery Consumption (@Simon):
    The battery impact is virtually negligible. When armed, Sentinel monitors the Karoo’s internal motion and accelerometer sensors without running heavy computations, screen rendering, or GPS routing tasks. During testing, leaving it armed over typical 15–30 minute coffee stops resulted in well under 0.5%–1% battery usage. You will not notice any meaningful drop in your total ride runtime.

    3. Bluetooth / Phone Disconnection (@Jakub):
    As Simon rightly pointed out, the device’s primary defense is local and autonomous. Even if Bluetooth disconnects because you step too far inside or behind thick walls:

    • The Karoo unit itself triggers the loud on-device alarm and visual flashing immediately upon detecting movement.
    • That local siren is usually more than enough to scare someone off or alert you and bystanders nearby.
    • If the phone re-enters Bluetooth range while the alarm is active, the alert notification will push to your phone immediately.

    Thanks again for the support, and ride safe!

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    Simon Lockwood

    Thanks @HesiOX

    Is this coming to the Karoo extensions library?

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    HesiOX

    Hi Simon! It's currently under review for the official Karoo Extensions Library — should be available there soon! 

    In the meantime you can install it manually:

    1. Download the latest APK from the GitHub releases page
    2. Transfer it to your Karoo via USB or the Hammerhead app
    3. On your Karoo go to Extensions → Install from file

    Hope that helps!

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