You shouldn't have variables in .h files, or you will get multiple declarations. You can put "extern" variables, and then have the real variables in a .cpp file. Making them static just gives multiple copies of variables of the same name, something you probably don't want.
I think the Wire library can be problematic, from memory of past experiences. The way the IDE copies stuff hither and thither it seems to need an include of Wire.h in the main sketch, seemingly when you shouldn't need it. Or at least it did under the 0022 version of the IDE.