The FretPen is an extremely miniature guitar that takes the form of a pen, making it much easier to crank out a tune absolutely anywhere. The tiny guitar has a single string and a fretboard made from real maple wood. When the pen/guitar handle is connected to a guitar-shaped base, it transmits sounds to a smartphone via Bluetooth, which can be made to sound like acoustic or electric sounds, as well as further adjusted from there.
The small FretPen is undoubtedly more portable than a full-sized guitar and if you're itching to get some practice in, it's great for strengthening your muscle memory, or try out on before you move to the real thing. The FretPens are still being crowdfunded on Kickstarter and if you're eager enough, there's still the chance to get one of these micro musical instruments at an introductory price.
The FretPen is a Writing Utensil That Doubles as a Miniature Guitar
Laura McQuarrie — April 30, 2014 — Life-Stages
References: kickstarter & gizmodo