I have seen these on a few bikes. What is the purpose :S
First off, track bikes cannot be slowed down by pedaling backwards. They are fixed gear bikes, which means that as long as the wheel is moving, the cranks are also moving (and vice versa). Track bikes are slowed down by using your leg muscles to slow down the rotation of the cranks. If you tried to 'pedal backwards' while moving at any decent speed on a track bike, you'd just hurt yourself.
Now, getting to the pad on the top tube, that is a protector that some riders use to protect the tube if it gets hit by the handlebars. Since there is no front brake or cables on the bike when one is racing, it's quite common, if one crashes, for the handlebars to rotate around and hit (and sometimes dent), the top tube. Track bars usually only have grips on the flat part of the drops, so you are risking metal to metal contact when that happens.
Do they add protection on a bike rack? Sure. Do they give your track bike some street cred? Definitely.