All BlackBerry applications use either Java RMS or RIM database APIs to store dynamic data. Ascendo applications optimize the space required, for example, Ascendo DataVault, our Password Manager for BlackBerry, allows the user to store notes for each item with a maximum of 10,000 characters per note. However, we store only the characters entered by the user, so if you enter a 100 character note, it takes 100 bytes. Ascendo Money and Ascendo DataVault include Desktop components that sync, backup & export which would allow you to offload data from BlackBerry if necessary.
As mentioned by djm2, you can determine the initial footprint of our applications by downloading them from our FAQ pages then right clicking on the file with the .COD extension to display the size (typically 150 - 300k).
Marc Ascendo Inc. Ascendo DataVault - Password Manager for BlackBerry Ascendo Money - Personal Finance Manager for BlackBerry