If you’re building a Raspberry Pi project and need to send data back-and-forth, the WiFi module built into newer Pi’s should be fine for most cases.
However, WiFi does not have a long range and also requires both investment (through your ISP) and setup (routers, access points, network security schemes).
If you’re deploying your project somewhere more remotely, without WiFi or a strong cellular network, like a farm, you’ll need another option. Something that can be deployed quickly with no overhead setup and that will transmit/receive over a long distance.
Eink, E-paper, Think Ink – Collin shares six segments pondering the unusual low-power display technology that somehow still seems a bit sci-fi – http://adafruit.com/thinkink
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