These videos show overlay buttons to control video speed. You can learn how to use the speed buttons in this guide - How to Use the Speed Buttons
Doesn't work with the Flash engine, neither on Android due to technology limitations, nor on devices without inline playback capability (iPhone...). Styling is in progress.
YouTube only supports the basic speed steps of 0.25, 0.5, 1.25, 1.5, 2, so it needs a special treatment:
Mixing Vimeo and YouTube: