Any App for Drawing on top of iMovie film?

Hi,

im trying to find an app or some software for Imovie which could allow me to draw with my mouse on to my moving films. Ive seen the FX used in adverts and music videos where flowers for example grow up buildings and are animated , coming to life over the actual film itself. Its not a cartoonr app but something obviusly a bit more advanced. Any ideas. It dosent even have to be for Imovie really I just want to source this product.

I want to make a music video and be able to draw things over me as if Im being covered in drawing.