In a few days, there is going to be support for API keys. So for example, if you have API key for administrator, you will simply attach to any URL:
?api_key=714552c6148e1617aeab526d0606184b94a80ec048fc09894ff1a72b740c5f19&api_username=administrator
And this will allow you to retrieve any resource (e.g. backup) without going through (or simulating) login sequence.