You can use SmartCard Manager to store your bank account numbers, credit card numbers, passwords and such data that you want to keep secret. You can insert a SmartCard (it is about the same size as a visiting card), into any Amida, which prompts for your PIN number, and then "unlocks" the data. Since only you have the PIN number, no one else can see your personal data or make changes to it.
At under Rs. 100, SmartCards are affordable enough for everyone in your family to have one (along with their own PIN numbers, of course)
SmartCard Manager in Action
Examples of personal data you can store securely
Details of your Internet Service Provider
Passwords on shopping sites, PIN numbers for credit cards etc.