Measuring all tariffs as a percentage of the goods' value is a prerequisite for further progress in talks about reducing trade barriers for agricultural goods.

ECONOMIST: Progress at last

Rich countries are loth to do more on farm trade until they see progress in talks on industrial goods and services.

ECONOMIST: 2005 will be a vital year for free-trade talks

They can then be exchanged for virtual goods in a game within the app, while friends' progress can also be tracked.

CNN: The wave of wearable computers