Apple's new video app is due out in April!
Clips is something of a cross between iMovie and Snapchat. You can edit together a series of clips and still images into longer videos that you can stylize with filters, text overlays, graphics, and, yes, lots of emoji.
Apple's app offers more flexibility. Your creations can be as short as a few seconds or as long as an hour (though, more likely, they'll be somewhere in between.