We appear to be entering a new golden age of electricity-free guitar amplification - earlier this year, we heard DelSonix's battery-less offering, and now Noggin Rockers hopes to provide a similar experience with headphones.
Noggin Rockers consist of a stethoscope-like appendage, which attaches to any surface of a guitar or bass via a separate pad, sending the sound of the instrument up to a pair of soft gel ear buds - no electricity or batteries required.
Volume and tone is controlled by loosening or tightening the device's diaphragm retaining ring: move it closer to make it louder, further away to bring the volume down.
They may seem low-tech, but Noggin Rockers could be handy for guitarists who are travelling light or precision tuning in a noisy environment.
Noggin Rockers are available now for $14.95 (plus $3 US shipping) from the company's website. NR promise it'll be the "best guitar amplifier you'll ever own for under $20", too, so could be worth a punt for the environmentally conscious among you.