This is the feature that (at least in an older version of Premiere Pro) allows one to animate video playback speed from slow to speeding up and even reversing or pausing all in a continuous gradation. Is this available by any means?
I have another link on that page to a template that you can download and study. It doesn't use the echo effect. It's just a series of very short clips that have each been timestreched a certain amount. I used the acceleration formula to come up the the values.