Design & Develop an Emoticon app on Android, iPhone, Windows & Blackberry

General information for the business: Emoticons for social media chat rooms like Whatsapp, FB, Twitter, BBM
Description of requirements/functionality: The main objective of the app is to allow users who have downloaded the app use the emoticons on their various social media chat forums on their phone i.e. Whatsapp, Twitter, FB, BBM text messaging etc.
The app should allow users to type certain texts on the chat and an option of a replacement icon to be displayed. For example, typing I LOVE you 'Love' should display a heart icon.
Only the users who download the app can use the emoticons. Other users can see the emoticon but won't be able to use it until they download the app.
The app will also have a form where users can leave suggestions on how to improve the emoticons.
The app should also allow users to review the app on the various platforms just once after download.
The app will have FREE emoticons but also paid for EMOTICONS i.e. having in-app payments
More information about the app will be communicated.
Extra notes: