“Use a pair of packet radios to draw and then send pictures between the two devices without WiFi or Bluetooth.
Reliance on certain wireless networks/protocols can add significant costs to a project, as well as limit how far away they can be. WiFi and Bluetooth both use the 2.4GHz band, which limits them to around 50-60 meters from an access point. This can be detrimental if all you want is to send a simple message between two points. Additionally, other protocols don’t have builtin encryption standards, which can leave messages prone to snooping.
This device fixes these problems. By using the RFM69 radio module, messages can be sent up to 500 meters away while also being encrypted with an AES-128 cypher.
The hardware required to build this project is quite simple and consists of three primary components: an Adafruit Feather M0 with RFM69 Packet Radio, a 128 by 64 pixel OLED display, and an analog joystick. From these items, a pair of identical devices can be created and used to pass messages back and forth. The entire thing fits on a single mini breadboard and could be easily adapted to a PCB format instead.”