I have a project idea that has the same concept as the USA house arrest device. But my project is for tracking children. My idea is to place a wearable device on the child that will communicate with an application to track and report the child's location. The app will also allow the parent to set boundaries in which the child can roam, and use a "google map"-like feature that displays the child's location. Also, the child's wearable device will set off an alarm if the child is about to breach the "safe location border".

I already have one raspberry pi 3 that I will use to make the wearable child tracking device. I also have things that are needed such as the GPS receiver, and alarm/buzzer etc.

My question is, "How will I set a center of a radius?" Should I get another raspberry pi that will be the center of the radius whenever the parent set a distance in the application? Also, if I get another raspi how will it work as a default center of a radius?

  • RPi 3 makes a terrible wearable device. There are smart watches which do what you describe and additionally allow parents to call the child from their cellphone, with everything crammed into 3x3x1 cm, including the battery. Commented Oct 31, 2018 at 13:52
  • Also, I don't understand the question. What the second RPi is for? Why not just make a small house-shaped button the user could push, which remembers the current GPS position? Commented Oct 31, 2018 at 13:55
  • Hi!. Btw this is my thesis. I have to make this and told already the function of my proj. I will test the project on several subject and different houses. And i dont know how will i put a center of a radius whenever the parent set the distance in the applocation. I will just clarify it there is an application where the parent can set sa radius in which the child is free to roam. The child device consist of raspi 3 and a gps + alarm. The alarm will alarm if ever the child is getting near the given parameter. The problem here is how can is set a default center of radius.
    – DniceGuy
    Commented Nov 1, 2018 at 15:01
  • As as I say before i will use it on different subject and different houses. Thats why im thinking to get another raspi where i can just set it any time any house so whenever the parent set the radius the 2nd raspi will be the center of the radius. Yet i am not sure if its posible since to be honest im not that familiar with raspi capability. Btw the 1st raspi which is a child device has a pocket wifi so i can send a data on the app realtime. Its just i dont know how can i set a center of a radius and im testing it on different places thats why im thinkjng 2nd raspi for the center of radius.
    – DniceGuy
    Commented Nov 1, 2018 at 15:04
  • If u have recomendation or idea it will help me alot tbh i really dont know what is the best way to do it. I been searching for the same proj or almost same never found one the motorcycle tracking is kinda different havent seen a proj where they uses app to set range and set radius like this 😔.
    – DniceGuy
    Commented Nov 1, 2018 at 15:10

1 Answer 1


It seems to me there are two general approaches to meet your objectives. Please note these are "general" approaches, and not intended to be specific in any sense of the word. You still have much work to do in your system design before you're ready to begin implementation:

1. Autonomous Approach:

Under this approach, you'll use two (2) RPi's as you've alluded. Both will have their own GPS receiver, and know their own location. The wearable device will communicate its GPS position to the "parent" device, and the parent device will communicate its position to the wearable device. Both devices can then calculate a distance and bearing to the other. Under this approach you wouldn't necessarily need Google's Map app; you could use OpenStreetMap as an alternative.

2. The Google Map Approach:

Under this approach, you won't need a second RPi; you'll only need the wearable RPi device with a GPS receiver. You'll create a software app on this wearable device that will query Google Maps with the GPS location (like this). Displaying the child's location on the parent's Google Map display can be accomplished through the "share my location" features.

Other Considerations:

Obviously you'll need to consider WiFi/Internet coverage for your device(s), and factor that into your system design. Without WiFi/Internet coverage, you'll need some sort of radio device, but that's an entirely different subject that won't be addressed here.

  • You don't really need to query Google maps to find the distance between current location and a given point. Even Cletus knows how to do it. Commented Oct 31, 2018 at 14:52
  • @DmitryGrigoryev: I'm struggling to find where I said Google maps had to be consulted to get distance, but the link to Cletus' post is a good one :)
    – Seamus
    Commented Oct 31, 2018 at 17:19

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