Form is an interaction prototyping tool, similar to Quartz Composer.
Form prototypes can be run on a real iOS device using the Perform companion app — resolving one of the biggest issues I had with Quartz Composer.
The parent company has been bought by Google, so I’d imagine an Android version is in the works as well. But I hope Google will continue their cross-platform Material design push and continue to support the existing iOS design tools as well.
Form is now free and definitely worth checking out: