A Hewlett Packard 48G scientific calculator has been hacked to be used as a Bluetooth ‘keyboard’ for a calculator app on a smartphone. The calculators guts were upgraded with an Adafruit Feather nRF52 Bluefruit board which added wireless Bluetooth connectivity. Programming each button to register clicks from its real-life counterpart was undoubtedly a time-consuming process, but the result is arguably a vastly improved emulated calculator experience for someone who can enter equations on one of these blindfolded.”]
Source: https://gizmodo.com/engineers-will-love-this-dead-calculator-hacked-into-a-1837312643