Please do not attempt this unless you can hold a stable plank with good technique on the floor for at least 30 secs and have also practised a swiss ball plank and feel confident and stable.
Swiss ball pikes and tucks are a good abdominal exercise and are also useful to training inversions such as handstands. If you are unsure ask someone to spot you with hands either side of your hips to catch you if you feel unstable. This exercise can also be done on a TRX system.