One very effective "ab" exercise is the Pushup to T-Hold. In order to do these, you'll need to be able to both do a proper pushup (chest to the floor, all the way back up, body in a straight line). These aren't that hard, really, but they aren't that easy. For some reason, Wii Fit seems to think these are pretty basic, but Wii Fit is really generous about what it counts as a pushup.
How do I do these? Get into a pushup position, go down and come back up. At the top, don't stop, but lift one hand off the floor and hold that arm straight up as you roll over into a side plank position. Squeeze your torso muscles and leg muscles to hold the position momentarily, and then return to the starting position. Repeat on the other side.
This video from Charles Staley shows one version, with both feet remaining on the floor.
This version involves rolling over on to the sides of the feet.
How can I make it harder?
First, do it as shown in the second video, but stack your feet as if you were in a side plank. This puts even more stress on your midsection. This is the only version I ever do. I feel it's both a little more difficult and a lot more effective.
Second, you can use dumbbells. Use a pair of hex dumbbells (or for the very brave and strong, round dumbbells or smaller kettlebells). These don't make the pushup harder, but do make the T-hold significantly harder. Be careful to slowly bring the hand up - don't swing the weight. Your shoulder is a complex joint, and the last thing it needs is a ballistically swinging weight pulling it back and out.
Third, you can use any usual methods to make the pushup harder, such as weighted vests or chains. Make sure you secure any chains to you tightly, so they don't slide off or down your body as you go into the T-hold.
What do these do for me? Try them and see. They really kill your midsection. They also give your shoulders a good workout, both from the pushup (dynamic strengthening movement) and the top hold (a static hold). The transition from position to position is just as important as either end of the movement, so do it slowly and under control. Your shoulder joint will thank you, and your midsection will improve in strength.
1 hour ago