Redirectoid is a very simple, easy-to-use server-side redirect script for MODX CMS that does what it says on the box and not a whole lot more.
As of version 2.2 you can invoke 2 special "modes" by passing-in a string instead of Resource ID to the
&id snippet property.
This will either naively pluck the first Resource from the array returned by
$modx->getChildIds() or via database query sorted by the
menuindex attribute. Note that it's possible to pass multiple parent Resource IDs to the Snippet, in which case a "tie" might occur and the database engine will return 1 based on internal ordering.
This invokes various pseudo-random methods to return a..well..random Resource within the constraints provided by the other Snippet properties. This feature has been available since version 2.x (many years).