Here's a quick code snippet for making JQuery's autocomplete ui element consume an OpenSearch resource:

    jQuery('#term').autocomplete('/proxy/opensearch', {parse: opensearch});
    function opensearch(data) {
        data = eval(data);
        var parsed = [];

        for (var i=0; i < data[1].length; i++) {
            var row = jQuery.trim(data[1][i]);
            if (row) {
                parsed[parsed.length] = {
                    data: [row],
                    value: row,
                    result: row
                };
            }
        }
        return parsed;
    }