This article is about the use of BLE (Bluetooth Low Energy) technology to hack and control various devices, including iMessage on iPhones. The author provides two sketches for using an ESP32 board to send a text message in someone else's last iMessage conversation and to broadcast constant stream of Bluetooth device notifications for under $25. The article also discusses the use of NimBLE-Arduino library to create BLE advertisements that can be used to annoy people or even hack into their devices. The author provides tutorials on how to install and configure the Arduino IDE, write sketches, and compile code using the ESP32 board. Additionally, the article mentions a security vulnerability in iOS that allows for arbitrary SMS sending via the `sms://` URL scheme.