Hear me out: the "Phone"-O-Graph passive smartphone amplifier is the most unique, stylish, and natural way to squeeze a few more precious decibels out of your smartphone's woefully inadequate bottom speaker without using any battery power or needing to connect to anything.  
Layers of American black walnut and white limba wood are laminated together into solid blocks from which the "Phone"-O-Graph's base and 'speaker' cone are crafted.
The 'speaker' cone is turned by hand on the Ohio Wood Art lathe.
Three rubber feet are screwed into the "Phone"-O-Graph's bottom surface to prevent it from moving around when what you're listening to gets particularly intense.
The Ohio Wood Art logo and maker's mark are laser-engraved into the back of the "Phone"-O-Graph. 
Finished with tung oil and furniture wax.
Smartphone not included.