What Is It?

apart from a rock,

 that weighs in at 1.5 tons and has a fire lit beside it, it is how you can charge your mobile telephone when there is no electricity or wi-fi,

 is actually a work of art called 'Keepalive' by Aram Bartholl, it’s a real boulder, but modified to hide a Wi-Fi router inside that is powered by a thermoelectric generator which converts heat directly into electricity, 

 so if you go to the peaceful village of Hartböhn in Lüneburg Heath in Germany you can try lighting a fire under the rock to see how it works, I wonder if a portable version is on the cards?