Formly - Collect data Anytime, Anywhere, even offline.
Fuse - Fuse is a UX tool suite for mobile app designers and developers.
Jotform - Free Online Form Builder & Form Creator
Siberian CMS - Siberian is an Open-Source and Free App Maker. Unlimited Push Notifications. Unlimited features. Fully Customizable. Download it and build your own app now!
FieldGoal - Don't build a whole backend just for one stupid form.
GoodBarber - GoodBarber is a mobile app creation platform.