The only way I personally could think of doing it is through variables. Set the variable to 50 to begin, and then have positive actions add one to the variable, and negative actions take away. For events and such, either set the conditions or use a conditional branch that says if Variable: alignment (or whatever you name it) is more than 50, Event 1 happens. If Variable:alignment is less than 50, Event 2 occurs. If Variable: alignment is exactly 50, event 3 happens (Neutral characters would react differently to situations than good or evil characters.
For the meter you referred to, use a bunch of pictures and branches, all on a common event.
If you want, I can try to throw together a mock-up event system.