Is there an IPhone app for putting videos/pictures over audio at different intervals?

It must be mobile, if not then please don't mention it because it will be of no use to me.

I want to take a video I have and keep the sound. Then put pictures and videos over the sound at different times.

For example at 0:36 a picture of A comes up, then at 1:00 it switches to a video of B.

I think iMovie should be able to handle that.