If you have a Moni account with sync enabled, you can export your data at any time for free.
Currently, it exports as a .csv file - which works fine for programs like Excel, Google Docs and most spreadsheet applications.
We'd like to hear if you have any other export formats you'd like to see. These are pretty easy to add, and won't clutter the app - so any suggestions are welcome!
Finally, we're planning to introduce an import option as well. If you have your existing transactions in another account and wish to transfer them, you currently have to do it manually. We need to build a Web Interface to allow for the upload, but it's in our pipeline.