I have scripted attachments that have to have timers to poll when outfits are changed. The polling is done using RLV commands (@getoutfit=channel) but may be useful in non-RLV situations.

Extend change event for attached only objects to include CHANGED_OUTFIT and CHANGED_ATTACHMENT when the avatar wears or removes clothing or attachments.

It would be up to the script to work out what has changed but would be more efficient than checking every few seconds.