Sounds cool right? yes you can hide the images that you have sent to your friends inside any other wierd images. Magiapp tricks App for Android and Fhumb App for iPhone allows you to hide the sent image inside other images.
This is how the app works, the image that you have sent is replaced with the other image, when they click on the image they will be seeing the orginal image. Unfortunately this trick won't work for Blackberry and Windows phones.
