What are some alternatives?
When comparing Spark Camera and Pretty Captions, you can also consider the following products
Quik by GoPro - Easiest way to create awesome videos
Captioned - Say, show, share. Create a 60 second captioned video.
Adobe Premiere Rush CC - Create and share online videos anywhere 🎬
Instaspacer - Putting the spaces back into Instagram
MotionDen - Free online animated video maker
Caption Writer for Instagram - Notepad for Instagram – but better.