Disclosure: I also have a similar thread running on the Arduino User Forum. Comments, there, have led me here.
Coding Partner for Very Small/Easy DIY Medical Equipment Retention Dongle - Projects Discussion and Showcase / Product Design - Arduino Forum
With minor edits, for clarity…
I have had to move into an assisted living facility. We wear emergency transmitter dongles that post directly to pagers that the nurses carry. The nurses often forget to leave their pagers for the next shift and take them home. This makes for a lack of coverage and that is a problem.
I would like to help, by building key fob style dongles that attach to the pagers and monitor stations that would be placed at each of the two doors. When a pager gets too close to the door, alarms would sound and blink.
I think the project is as simple as tiny MCUs talking to each other over Bluetooth. The key fobs would constantly transmit their identity code. The monitors would constantly listen for the codes.
IIUC, this Seeed ESP32C3 might have all of the MCU power and BLE functionality that is needed for both the monitor and the key fob. And, they are cheap enough…
Amazon.com: Seeed Studio XIAO ESP32C3(Support Arduino) - Tiny MCU Board for IoT Controlling Scenarios, Wi-Fi, BLE, Battery Charge, and Rich Interface for Tiny Machine Learning : Electronics
This project could be used for all sorts of purposes… Keeping infants, dementia patients, or pets inside… Retaining expensive company tools… Anything that you need to keep track of.
I have considered RF anti-shoplifting tag systems. The tags are cheap. The monitors are very expensive!
I am thinking of using Bluetooth, because the monitor stations only need a range of maybe 3 to 6 feet. WiFi would have too much range.
So, I purpose to build the hardware (KiCad to PCB to working units,) or assemble various ready made modules, if you will write the code, or help me assemble the firmware/software systems from OS Code units. (I do not code and I am too old to learn. But, I know how the two interface.) Then, we will distribute it as open source. I will finance the hardware costs. Or, if someone knows of this project as fully developed, I would appreciate the link.
I look forward to working with you.
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I have learned that readymade BLE key fobs are available, for a very modest cost. And, repurposing old computer gear, or using Raspberry Pies, or small MCUs/ESP32C3/Arduino Uno R4-BLE/Wifi also saves cost. I can gather those things quickly. But, I would need someone to get them to talk to each other - meaning, the complete firmware/software integration.
I hope that you will join in. If you are not able to, perhaps you could provide me with the link to a complete project that performs similar functions.
Thank you, for your help!!!