Is there a remote transport controller that can control tempo?

I have had a call from a friend of mine who wants to control a laptop running a DAW program live. (Not exactly sure which one yet) Is there a transport controller out there that allows for tempo control as well as normal transport functions? This might be harder than just transport control only. It might require a device that can generate a clock and take over the DAW in question. Not sure. Or is it easy to program buttons easily to alter tempo (in Sonar) either in an upward direction or downward direction on a control surface.