I've used Google 2-Step Verification for months to protect my Google Apps logins, using the Google Authenticator App on my phone. However, a good friend just pointed me to Authy, which supports additional apps including Dropbox, Facebook and others. It bills itself as Two-Factor Authentication without the hassle, and I agree! What I missed immediately though was connecting back into my MailChimp account.
A quick search for "Authy MailChimp" gave me nothing. Turns out, though, it's not so hard.
By the way, there's a couple of reasons to use two-factor authentication with MailChimp. First, it's a lot more secure—so really you should use it with everything possible. Second, you get a discount off paid plans at MailChimp. We save $15/month or so.
Simply login to your AlterEgo account, and disconnect your Google Authenticator App. Connect it again and use the Authy iOS app to scan the barcode that pops up. For the account type, choose Gmail, and that's it.
I pinged MailChimp to let them know this works, and emailed Authy, too.
Hopefully we'll get a proper icon soon. update: You can choose an alternate icon, using "Other" which is just a nice little key icon. (Not sure if this is an option during scanning the QR code though, and it's set up now so will save that experiment for another day.)