The wbapi module provides a request handler that takes the supported arguments to the query and then formats them properly, sends on the GET request to the API server, and returns the result as a PHP array.
The included wbquery module builds Views 3 handlers atop this functionality, allowing basic views to be created through the standard interface, with the wbapi serving as the backend in lieu of the standard MySQL stack. This behavior was made possible by the pluggable query objects of Views 3, thus it doesn't work at all with Views 2; see that module and its READMEs and issue queues for more detail.
Additionally, as Views 3 is still in alpha, its API is changing--this can lead to fatal errors in this module if you use an unexpected version. Thus, releases of this module will correspond to the views version with which they are compatible. The current ALPHA3 release therefore corresponds to the latest Views 3 ALPHA3 release. When views has another release, we will try to release a corresponding new version of this module to work with it.
If you use this module and add additional functionality, we are very receptive to patches adding further handlers to wbquery or additional functionality to wbapi. The module is stable and functional, having been already deployed in production to power all the data views on http://data.worldbank.org, a site that demonstrates the API's capabilities.
The development of this module sponsored by the World Bank as part of the Bank's Open Data initiative and the http://data.worldbank.org site.