Could you please add record button skin customization to your perfect application?
Please do it simple: for example, skin image should be in .png format only; button dimensions == (skin image height) x (skin image width/2), first half is for unpressed button, second for pressed.
Also will be great if you add small predefined skin library for the built-in phone apps from the most prime phone manufacturers. This will make your call recording button pretty stylish ;)