Hello, I'm Vishal. I made Reactions.
Let me walk you through what it is.
Reactions is a bundle containing an iOS and an iMessage App. All emojis supported by iOS devices are indexed and are searchable within the Reactions apps. Every emoji is associated with related names and tags. Emojis of every color scheme is supported, too.
The iMessage App provides stickers for all emojis. This enables you to react to messages with an appropriate emoji sticker. Since all emojis are searchable not just by their names, but by many related words and tags, finding the right reaction to a message is very easy. Reactions also supports adding custom names for all emojis.
The main iOS App works as a directory for emojis on your device. You can search, manage, copy and add custom names to emojis as much as you want. The changes will reflect on the iMessage App as they both share a common database on the phone.
Since Reactions is integrated with Spotlight on iOS, you can search for reactions on Spotlight and derive results instantly. With just a couple more interactions, you can copy that emoji and use it anywhere. This means that you don't even have to open the app for finding the right emoji.
Reactions also lets you copy every Reaction as either text or an image for more versatile usage.
Ultimately, Reactions will allow you to better search for the right reaction for any instance. Since it stickerizes the emojis, it's fun to use the well-known emojis in conversations.
Update: Apple rejected the app due to copyright violations in using emojis graphics that are owned by Apple. I need to take another look at the review guidelines and tweak my app to pass through the review process.
See Reactions on Twitter