Not use any device that has GSM/LTE, or Bluetooth.
Alternatively, broadcast a hidden SSID WiFi AP via an enabled RPi and use only devices that's have WiFi. Hand them out to people for free to increase the spread.
Attach magnets to the RPi's and go rogue by sticking them to buses, cars and trains et cetera to increase range.
Are there decent wifi communicators on the market? I looked into some Lora projects for this but they never seem to actually ship or get past prorotypes
> Are there decent wifi communicators on the market? I looked into some Lora projects for this but they never seem to actually ship or get past prorotype
Yes, 100%. Meshtastic and Meshcore both do this, but I'd recommend Meshcore. Here in the Seattle area we have a network that fairly reliably delivers messages from Canada through the Seattle metro area all the way down to Portland. Fully encrypted with dual key cryptography. Meshcore uses a different strategy than Meshtastic, which enables Meshcore to work more reliably. To see what's happening in your area for Meshcore see https://analyzer.letsmesh.net/map
Is very fun to set up a repeater for under $50 and see a noticeable difference in the coverage area. Is a fun technical project that combines the best of hiking/walking/driving geocaching style, ham radio (but without a license requirement), antenna building, and more. I'm getting acquainted with people in my neighborhood too which is a bonus.
Figuring out what hardware to buy that'll actually work can be a challenge, to get started search amazon for "heltec v3" and make sure you get something that includes a battery, and you'll see 2-packs of radios for $60. There's a web flasher at the above link that'll put the software on the radios for you.
Really wish more people would get on the Meshcore train here locally. Everyone just picked up meshtastic and looked no further.
Meshcore's crypto is interesting.
ECB, issues with key generation, key negotiation, seldom authenticated data, ...
It definitely works better than MT but please stop lauding it for its cryptographic properties ;)
It's at the bottom of their TODO, under the heading "V2 protocol spec".
> a hidden SSID WiFi
Don't do this!
The BSSID is still visible, and is the unique identifier any trackers will be looking for anyway. Also making the SSID hidden just means the AP isn't broadcasting it, any listeners can still see the SSID whenever any client interacts with the AP.
Hidden SSIDs are generally much worse for privacy than non-hidden ones, since all stations (clients in 802.11 terminology) need to constantly go around yelling "hey, is SSID abc available?" while they're not connected to any SSID.
I was ultimately taking the piss, it'll be radical if someone actually did but I had no idea it caused wifi pollution from this.
You learn something new everyday.