selectedRowIndices

Returns a dictionary, containing the view and data source indices of the currently selected rows.

$("#grid").shieldGrid({
    dataSource: {
        data: [
            { ID: 1, name: "name1" },
            { ID: 2, name: "name2" }
        ]
    },
    selection: {
        type: "row"
    },
    columns: [
        { field: "ID" },
        { field: "name" }
    ]
});

// select the first row
$("#grid").swidget().select("tr:eq(0)");

// returns: { view: [0], data: [0] }
var sel = $("#grid").swidget().selectedRowIndices();