var LastID;
function QueryLastNewStatusItem() {
    var clientContext = new SP.ClientContext();
    var List = clientContext.get_web().get_lists().getByTitle('Tracker');
    var query = new SP.CamlQuery();
    var textCaml ="
        <View>
        <RowLimit>1</RowLimit>
        <Query>
            <OrderBy>
            <FieldRef Name='ID' Ascending='False' />
            </OrderBy>
            <Where>
            <Eq>
                <FieldRef Name='Status' />
                <Value Type='Text'>New</Value>
            </Eq>
        </Where>
        </Query>
        </View>";
    query.set_viewXml(textCaml);
    var item = List.getItems(query);
    context.load(item);
    LastID = GetItemID(item);
    alert(LastID);
}