I'm not sure when the goblet was invented. I'm sure it's also undocumented when someone first ran their finger along the rim of one and produced a sound. Then later yet someone would have figured out how to tune them, and put them together so that they could be used to play a melody. That last person arguably was the first glass harper.
Leave it to Ben Franklin to come up with a better way. According to the WSJ, his favorite invention was the armonica. It was constructed of glass bowls that were nested and mounted concentrically on a horizontal shaft which could be rotated. Thus the musician need only move his hand from one to another to play another pitch without the complication of sliding his fingers along the rim.
With modern synthesizers being as cheap and powerful as they are, I'm guessing that we won't be seeing any further development with this. That's OK with me - somehow automating this any further seems to be missing the point.