Filter users by meta in BP Members Directory

<?php
/**
* as i test on bp members directory
* i first add a new option in member filter
* it could be the score user meta_key in your case
* in mine it's the latest geo position user meta_key (bpci_latest_address)
*/
add_action( 'bp_members_directory_order_options', 'bp_imath_experimental_add_umeta_in_filter_list');

function bp_imath_experimental_add_umeta_in_filter_list() {
    ?>
    <option value="bpci_latest_address"><?php _e( 'Latest Geo Postion', 'buddypress' ); ?></option>
    <?php
}


/**
* the main trick is to directly apply a filter on the request
* that BP_Core_User::get_users will play
*/
add_filter('bp_core_get_paged_users_sql', 'bp_imath_experimental_umeta_filter_select', 10, 2);

function bp_imath_experimental_umeta_filter_select($query, $sql) {

    /* check the meta before modifying the query...*/
    if( !empty($sql['where_meta']) && strpos( $sql['where_meta'], 'bpci_latest_address') >= 0 ) {
        /**
        * by default the ORDER BY is on um.meta_value
        * but our meta_value is umm.meta_value, so we need to change this!
        * you can also change the order (DESC or ASC)
        */
        $sql[0] = 'ORDER BY umm.meta_value DESC';
        $sql['select_meta'] = ', umm.meta_value as position';
        $query = join( ' ', (array)$sql );
    }

    return $query;

}


/**
* we must also filter the count request for pagination
* that BP_Core_User::get_users will play
*/
add_filter('bp_core_get_total_users_sql', 'bp_imath_experimental_umeta_filter_count', 10, 2);

function bp_imath_experimental_umeta_filter_count($query, $sql) {

    /* check the meta before modifying the query...*/
    if( !empty($sql['where_meta']) && strpos( $sql['where_meta'], 'bpci_latest_address') >= 0 ) {
        // you can change order by pref (DESC or ASC)
        $sql[1] = 'ORDER BY umm.meta_value DESC';
        $sql['select_meta'] = '';
        $query = join( ' ', (array)$sql );
    }

    return $query;
}

/**
* as i play directly on the members directory
* i need to filter the ajax querystring to add the meta_key argument
* meta_key=bpci_latest_address
*/
add_filter( 'bp_dtheme_ajax_querystring', 'bp_imath_experimental_dtheme_ajax_query', 10, 7 );

function bp_imath_experimental_dtheme_ajax_query( $query_string, $object, $object_filter, $object_scope, $object_page, $object_search_terms, $object_extras ){

    /* check filter before modifying querystring...*/
    if( $object_filter == 'bpci_latest_address' ) {

        if( strpos($query_string, 'type=bpci_latest_address&action=bpci_latest_address') >= 0 )
            $query_string = str_replace('type=bpci_latest_address&action=bpci_latest_address', 'meta_key=bpci_latest_address', $query_string);

    }

    return $query_string;

}

/**
* now as i added 'umm.meta_value as position'
* in the select query, let's use this value
* instead of using echo get_user_meta( $user_id ,'bpci_latest_address', true)
*/
function bp_imath_experimental_the_member_position() {
    echo bp_imath_experimental_get_the_member_position();
}
    function bp_imath_experimental_get_the_member_position(){
        global $members_template;

        return apply_filters('bp_imath_experimental_get_the_member_position', $members_template->member->position);
    }

/**
* finally let's display the position or score in your case..
* by using the hook just after the latest activity in the members-loop template
*/
add_action('bp_directory_members_item', 'bp_imath_experimental_finally_display');

function bp_imath_experimental_finally_display(){
    ?>
    <div class="whatever"><?php bp_imath_experimental_the_member_position();?></div>
    <?php
}
?>