Delighted is wonderfully simple solution to collect NPS. While not very customisable it is stable, easy to set up and has a very nice API.
We integrate with Delighted via their API, fetching all responses periodically.
To set up an integration please send your Delighted API Key to your Chattermill Account Manager or to our support team. You can find your API Key via the Settings page. Please contact Delighted support should you have problems locating it.