Filter (Search) by PHP field

This excellent module has given me the ability to access data in views that is not normally accessible with standard fields.

I've actually been using this module with node_load($row->nid) then retrieving the data I need from the $node array with a delta value as the array index for multiple value fields or by looping through the array until I find the value I need.

The only shortcoming is that I cannot filter or search by the output of this field. Is there currently any way to do this? If not, what might be involved in getting this feature working?