Just like a smart phone vagenius relates to the level of features a woman's vagina has. Most men appreciate and cherish vagenius. Generally, it is meant as a high form of praise toward the level of quality of the woman's vagina.
Some features common to vagenius's are: snap back, kegel lock up, squirting, pussy tricks in general. It can also be applied in a sentence such as she got some "vagenius!" or She pays the bills with her "vagenius - (smart pussy)".