Not sure if all the Huggies diapers have wetness indicators but I do know that the Huggies Snug and dry diapers that my 3 year old nephew wears all the time does.
It lets his parents and us know that he needs a change without having to feel the diaper.
I'm pretty certain though that Huggies has it's Wetness indicator on all it's line of diapers though and it's very useful to just glance at the diaper and see if it's time for a diaper change.
My nephew hardly wears any pants around his house or even my house when I'm watching him so he mostly wears just the diaper and a shirt because he hates pants or shorts so it makes it easy for us to check his diaper.