They’re all a similar configuration of a relatively large amount of memory (compared to the usual embedded computer), a WiFi chip, and an ARM processor running a tiny Linux install. The card ...

WiFi signal strength indicators show how strong your connection is. The credit card chip helps keep your transactions safe. Contactless payment symbols mean you can pay without swiping your card.

You can find commercial USB sticks that can also connect via WiFi. But [Neutrino] made his own using an ESP8266 married to a card reader. It all starts with the old trick of soldering a header to ...