"it is free and always will be"
Only for Android 4.3.1 and lower :
Ice Cream Sandwich (4.0–4.0.4)
Jelly Bean (4.1–4.3.1)
******(Important : Android 4.4 and above users look on the information in the bottom)****
In this application you can copy all your Whats Application media files (Video Pictures and Audio file) from the internal memory the default place Whats Application put it in to the external SD card.
By doing that you can free all the memory from your phone and keep all the images videos or audio on your external card.
On android 4.4 to 4.4.4 the ability to copy files to SD external card is disabled so to do so you need to do couple of steps that written in the application the app designed for 4.3 and under but yet you can use it on all Android.