Unfortunately, [Unicoins seem to have been retired for now](http://meta.stackexchange.com/questions/227363/what-are-stack-overflow-unicoins), and the current revision of the API (2.2) does not support anything even remotely currency-related, unless you count Bitcoin Stack Exchange. (We can still dream about the inclusion of Unicoins in 2.3 or 3.0, though.)