How to build a roll call IoT app?

Question

I've brainstormed an idea for an IoT hobby project but don't know exactly where to start in terms of the implementation. Here's the idea. 10 of my friends who live <.5 mile radius of my house like to get together often. I want to give all my friends each a small clicker ( or the like) to report to me whether they will be able to attend an outing. So for instance, on Sunday morning each friend will 'click' to inform me whether they will come later that afternoon. What is the most appropriate protocol to use? What type of hardware will I need?

Answer 1

This is a very broad question with lots of possible answers, but here are three possible approaches:

• Pure software: an app or a website they can use on their mobile.

• Hardware solution, direct link to your home: given the distance and very likely obstacles, this is probably not possible using WiFi and even less with BLE. You would need a device using a protocol that supports longer distances like LoRa, but even then, obstacles on the way can radically change the feasibility. If you want to go down this road, there are plenty of boards with an ESP32 and LoRa radio. Add a battery, a decent case with a button, and write some simple software that will put the device in deep sleep, set to wake up on button press, on which case it will send a message over LoRa and go back to sleep. You’ll need a device at your home to receive those messages and act upon them. Watch out for packet loss.

• Hardware, using local network: the easiest option is probably to connect to the local Wifi. Other than that, the approach is the same as above in terms of the device (but there are even more ESP32 boards without LoRa), and here you need a server reachable from the Internet to receive the messages.

There are other alternatives involving a board with a cellular modem instead, and some would probably suggest WiFi HaLow or other radio protocols.

There are of course a lot of details and caveats in each option, but this should get you started until you come up with more specific questions.