In case you were thinking about tinkling over your smartphone, the process isn't that simple. The urine needs to be in contact with a Microbial Fuel Cell, which consists of microbial organisms that break down the urine and turn it into electricity. The process even results in less toxic urine, making it safer to dispose of.
Right now, the one problem that the scientists working on the project have run into, is putting enough of these Fuel Cells together to produce enough electricity. But as the work continues on this project, there is hope that someday, you can charge your phone by recycling that six-pack you consumed earlier.