[Paul Gallagher] has the answer in one case, he’s used not one kit but two of them as for a guitar tuner project. At its heart is a Boldport Cuttlefish ATmega328 development board, and for its ...

Both the App Store and Google Play are replete with guitar-tuning apps that are full of either upsells or advertisements. Isn't there any application that helps tune your guitar without bothering you?