All */iframe endpoints, survey/all, and surveys/list now accept a parent_window_origin parameter to enable an iframed webform to post messages to its parent window.
Messages currently supported are:
{ enketoEvent: 'submissionsuccess' }
and
{ enketoEvent: 'edited' }
demo: http://enketo.github.io/enketo-iframe-demo/
The returned URL contains the 'feature' (and it is not stored in Enketo's Database), so a single survey can be iframed on multiple domains by making multiple different API calls.