Product Fit - Measure product/market fit in app with your users.
Interactive NPS Calculator (by Delighted) - Calculate your NPS easily with this interactive free tool.
Viable Fit - Measure and improve your product market fit
TinyNPS - Simple NPS feedback
YesInsights - Get Customer feedback with simple one-click or NPS surveys
Delighted + NomNom Integration - Turn your NPS responses into product insights