I haven't used PhoneGap yet, but they claim that you develop apps with plain old JS, CSS, and HTML.
If that's true, then use the API just like you would from a web page -- with simple AJAX calls.
Here's a working example (using jQuery):
var userID = 1416412;
var pageNum = 1;
var pageSize = 100;
var siteParam = 'stackoverflow';
var appKey ...