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if on windows, check out http://winauth.com you can save the .xml and exe on to google drive so that you can access it from any windows pc.
Also, if you have an android phone, Flex Auth is from the play store, and you can store all the bnet accounts you wish. you can use the secret keys from one of the apps to transfer to the other program. I just dont remember which direction you need to do it from as its been a while since i've had to add any.
FlexAuth works fine for me on battle.net