This is a small issue that has tripped me up before, and which was also reported to me on Twitter. The syntax to get the bindingContext in a list view item's tap handler varies based on the type of element you use. Here's a short example:

<Page loaded="loaded">
    <ListView items="{{ myList }}">
        <ListView.itemTemplate>
            <StackLayout>
                <Button tap="buttonTap" text="Hi, I'm a button" />
                <Label tap="labelTap" text="Hi, I'm a label" />
            </StackLayout>
        </ListView.itemTemplate>
    </ListView>
</Page>

var observableModule = require("data/observable");
var observableArrayModule = require("data/observable-array");

var pageData = new observableModule.Observable({
    myList: new observableArrayModule.ObservableArray(["foo", "bar"])
});

exports.loaded = function(args) {
    var page = args.object;
    page.bindingContext = pageData;
};

exports.buttonTap = function(args) {
    console.log(args.object.bindingContext);
};
exports.labelTap = function(args) {
    console.log(args.view.bindingContext)
};

The thing to notice here is that buttonTap uses args.object.bindingContext, whereas labelTap uses args.view.bindingContext to get a reference to the same data.

It seems like the API should be the same regardless of what type of UI component you use. A consistent approach would also make it far easier to share code.