What on earth can you possibly do with one string and 3 frets? Not much of course, unless there’s a bit of digital magic thrown in. The FretPen is a fully functional writing instrument, but it’s also a smartphone-connected one-string guitar. You clearly won’t be able to recreate Slash’s solos from November Rain, but a tiny D-pad on the pen does allow you to switch strings on the fly, giving you the ability to play scale-like runs and some forms of rudimentary melodies. If you watch the video below you’ll get a sense of the device’s capabilities. There’s a Kickstarter campaign launching on the 22nd, so if this piques your interest, feel free to give them your email address to be notified when they’re ready to accept your pledges.