BE Modded: Exploring and hacking the Vital Bracelet ecosystem

The Vital Bracelet series is an ecosystem of interactive fitness toys, content on memory chips, and apps that talk via NFC. In this talk, we'll explore the hardware and software of the series, from its obscure CPU architecture, to how it interacts with the outside world, from dumping OTP ROMs and breaking security, to making custom firmware. The Vital Bracelet series, active from 2021 to 2024, was a line of toys that revolved around a number of fitness bracelets that encouraged exercise by raising characters from the Digimon series, and expanding into tokusatsu and popular anime characters later. Think of it as Tamagotchi, but nurturing through exercise instead of button presses. In this presentation, we'll look at the different parts of this series' ecosystem, how they work, and the different ways to circumvent various security measures and customize the devices' behavior. We start by looking at the first Vital Bracelet, with a quick introduction to hardware reverse engineering and