this is one, which I did this days.
It is runnung on all resources with given migxtv_templates (3 and 7)
It stores all configured Text-fields of configured MIGX-TVs into a target_tv.
The target_tv could be at the same resource (if the template matches the given template)
or into a child-resource, which matches the given template.
This was for a special setup, where some of the MIGX-TVs was not listed at the same resource, but at a child-resource. Normally this option isn't needed.

It reads also nested MIGX - TVs, example here, the field 'downloads' with type 'migx' in the migxtv3.

<!--?php

$migxtv_templates = '3,7';
$config = '[
{"tvname":"migxtv","template":"3","target_tv":"searchMigxData","fields":[
    {"field":"headline"},
    {"field":"text"}
]},
{"tvname":"migxtv","template":"7","target_tv":"searchMigxData","fields":[
    {"field":"headline"},
    {"field":"text"}
]},
{"tvname":"othermigxtv","template":"4","target_tv":"searchMigxData","fields":[
    {"field":"headline"},
    {"field":"text"}
]},
{"tvname":"migxtv3","template":"5","target_tv":"searchMigxData","fields":[
    {"field":"headline"},
    {"field":"text"},
    {"field":"headline_bundle"},
    {"field":"downloads","type":"migx","fields":[
        {"field":"title1"},
        {"field":"title2"},
        {"field":"text"}
    ]}
]}
]';

function jsonFieldsToArray($items, $fields) {
    global $modx;
    
    $output = array();
    if (!is_array($items)) {
        $items = $modx--->fromJson($items);
    }
    if (is_array($items)) {
        foreach ($items as $item) {
            foreach ($fields as $field) {
                $fieldname = $modx->getOption('field', $field, '');
                $type = $modx->getOption('type', $field, '');
                if (isset($item[$fieldname])) {
                    if ($type == 'migx') {
                        $subitems = $item[$fieldname];
                        $subfields = $modx->getOption('fields', $field, '');
                        $suboutput = jsonFieldsToArray($subitems,$subfields);
                        $output = array_merge($output,$suboutput);  
                    } else {
                        $output[] = $item[$fieldname];
                    }
                }
            }
        }
    }
    return $output;
}


$migxtv_templates = explode(',', $migxtv_templates);

$resource_template = $resource->get('template');
if (in_array($resource_template, $migxtv_templates)) {

    $config = $modx->fromJson($config);
    foreach ($config as $cfg) {
        $tvname = $modx->getOption('tvname', $cfg, '');
        $template = $modx->getOption('template', $cfg, '');
        $fields = $modx->getOption('fields', $cfg, '');
        $target_tv = $modx->getOption('target_tv', $cfg, '');
        $items = $resource->getTVValue($tvname);
        $values = jsonFieldsToArray($items, $fields);
        if ($template == $resource_template){
            //has the template itself - we save to that resource
            $resource->setTVValue($target_tv,implode("\n\n",$values));
            
        }elseif ($target_resource = $modx->getObject('modResource',array('template'=>$template,'parent'=>$resource->get('id')))){
            //otherwise search child-resource with that template
            $target_resource->setTVValue($target_tv,implode("\n\n",$values)); 
        }
    }
    
}

Damn will have to buy you a beer again... **mumbling whilst clicking the sponsor link**