Do you use two-factor auth at all? If so, using an app like Google Authenticator or Authy or how 1Password, is an alternative way of receiving the two factor auth token that they would otherwise send via SMS. If the service (like Dropbox) allows you to use an Authenticator app, to set it up you go to the website and it shows you a QR code. In the app, you use the camera to scan the QR code and then it is linked to the website/service. Then if I use Dropbox on a new PC, and I need to get the two factor auth token after entering my password, I open the Authenticator app and I get a six (or so) digit code to enter as my two factor auth token.
If you don't use two factor auth, you should and let me know if you need an explanation of it.