I looked at all the NPS solutions out there. Some are nice, but none matched how I thought about NPS.
Most are focused on continuous NPS where I prefer to send surveys quarterly or semi-annually. All were exorbitantly expensive.
We've run HelpSpot profitably and without outside funding for over 12 years. That means I get to take little adventures from time to time. Thermostat is one of them!
I hope you'll join me in bringing NPS to more businesses and organizations.
P.S. I'm publishing some of the more useful mailing list info to our articles section. Check that out if you haven't yet.