Supports an unlimited number of AWS accounts. Accounts can be configured using simple auto-configuration, which sends you an email with a CloudFormation link to create an IAM user that has access to billing information. Or you can manually enter an AWS Access Key Id and Secret Access Key that you manage yourself.
The application tracks your billing amount by making calls to Amazon's Cost Explorer service, which will generate a tiny amount of costs in itself. For this reason the billing amount is updated automatically no more frequently than once per day. Due to how Background Execution works, the exact time of day may vary.
Auto-configuration details: When you open the CloudFormation link in a web browser, you will be asked to sign in to AWS. At this point you may choose a region or use the default. The CloudFormation stack creates an IAM user with the appropriate access rights and an access key. It then executes a Lambda function which uses AES-256 to encrypt the access key and sends it to Clouden's intermediary service. The iOS application then retrieves the access key, decrypts it, stores it on the phone in a secure keychain, and deletes the encrypted access key from Clouden's intermediary service. The original CloudFormation template is also automatically deleted from Clouden's intermediary service, so no data is left lying around.
Manual configuration details: When you manually enter an AWS Access Key, it is stored on the phone in a secure keychain and only used to sign AWS Cost Explorer API requests.