Ask HN: Feedback on an iOS Messages App

I am trying to create what I consider a useful iOS Sticker App for a use case that I constantly, which is the ability to annotate or point out pertinent information in a Messages thread. I've created and released my first go at an annotation sticker app and was wondering if HN can provide any suggestions or advice for different types of stickers they would find useful.

Here is a link to the app: https://itunes.apple.com/us/app/annotate!/id1161173401?mt=8&ign-mpt=uo%3D4

It does cost $1.99, since I am asking for feedback, I've provided some promo codes here: http://codehookup.com/42a011ed (if the run out, let me know and I'll put some more out there).