Create my own custom keyboard with my own images

On Android, I need to create my own IME which lets users to choose an image and send it right away to the already open WhatsApp, Email, Facebook, etc window, without showing any extra chooser (cause we're already working with the contact we wnat to send the image to).

To have a better idea, it should work as an emoji keyboard but using my own images, similar to the Ikea emoticons app.

I've already tried with Intent, but couldn't find a way to point it to the already active contact window.