Cashculator exists in Mac version as well, with "what-if" scenarios, more detailed transaction entry and additional extended functionality. It costs more as well :-)
Unfortunately currently Cashculator for iOS and for Mac are two separate applications that can't share data, so for now you will have to pick one of them to manage your finances.
Our goal is to bring them together and allow synchronizing data between these applications using iCloud. This way you will have access to your Cashculator data on the fly with your mobile device, but you will also be able to access more advanced functionality of Mac version. It will be achieved in Cashculator 2.0, that we're currently working on and expect to complete in second half of 2012.
Currently Cashculator doesn't support iCloud, but we plan to add that functionality soon. If it's important to you, you're welcome to let us know about it so that we could prioritize this effort.