Solar Powered Portable Gadgets

Solar-powered headphones for eternal playtime. Can be charged by any light (indoor/outdoor). This can be further improved and implement on other devices (importantly smartphones). "I remember the Casio calculator". 

 

 

(Source: https://www.digitaltrends.com/home-theater/adidas-rpt-02-sol-gustaf-rosell-zound-industries-interview/?utm_source=reddit&utm_medium=web&utm_campaign=pd)