I have used AB Roller Wheel and Knee Protectors Set as part of my core training.
. You can do push/pull version of the basic wheel roll-lout. When you push the wheel out, in the extended position and hold that position for several seconds, you are doing a resisted plank. You then reverse your position , get in the extended roll out and make sure there is some resistance on the wheel. the you pull the the wheel in and hold in the contracted position. Do 10-20 reps of both exercises, and three sets. You will feel the burn! This wheel is also good for wood chop (high or low)