Buvty - Yes, the radio test is a problem, as could be buvti or maybe bufty.
Vumiu - Again, radio test is a problem. How do you pronounce it? Would you pronounce the ending like the Greek Mu?
I would not choose either of these words as a brand name because of the spelling issues. That said, you never do know, and you could put them on BrandBucket and hope.
Good luck!