Michael Ossmann set out to make Bluetooth sniffing cheap and easy. Because of the way that bluetooth works (watch the videos if you want the technical details) there will never be a consumer product with any kind of monitoring or sniffing mode. The only hardware options when he began the project cost around a thousand dollars. So, he began to design an "open source bluetooth sniffing platform" that was relatively cheap and portable. Having never engaged in any sort of digital circuit tomfoolery prior to this project, he started with knowledge of Ohm's law, V = IR. And, ended up with these nifty little dongles.