Authy, Google, and Dropbox all adhere to the same pre-existing open standard. This just lets you generate different auth keys for different tokens from the same app, instead of having to have multiple native apps (Dropbox, Google Authenticator, etc) to each generate their own key using the same algorithm.
EXACTLY!
Not to discredit Authy here, given they're admirably embracing the open standard, but Google Authenticator happily takes any OTP code.
But their iOS app is 1000x uglier. Swapped my Google Auth credentials into Authy as soon as I realized I had the option.