Complete level 3 in Dragon Walker mode to unlock Vegeta's Scouter. A scouter appears as a semi-transparent colored monocle that covers the left eye and it's purpose is to calculate the individual power level or ki concentration of biological characters by converting the readings into numbers.
when your health is not at maximum, go to pause menu and if you have items: sacred water or ultra divine water, add it to character and exit. if you still don't have maximum health choose default, exit menu, go back and choose customize again, till' health is at maximum. it really works! i tried it my self!
Complete the game and replay the chapter where you become Vegito. When it gets to the part where you become Vegito, you'll instead be asked to play as either Vegito or Gogeta. Pick Gogeta and win to unlcok him.