i found this a while ago but i forgot to share it, maybe you allready have an application for this but this one i think is one of the best and i found it very usefull
the cool thing about it is that it has tetrad, analogic and accented analogic options and it also shows you lighter and darker color tints for each color...yes it;s a color wheel, but one of the finest
check it out here
[link]
Superb tool... helps me a lot in choosing a colour palette for my paintings!