Question custom keyboard on password fields?

More and more websites are requiring numbers, symbols, and capitals in their passwords.

Is there any app (or is it even possible to write an app) that would automatically switch keyboards when the focus enters a password field.

I like the Android L keyboard a lot (and swype, swiftkey, fleksy, etc...) but none of them are good for entering passwords.

However, there are some keyboards that are EXCELLENT for passwords and I thought it would be useful to automatically toggle to one when you enter a password field. For example: Hacker Keyboard

Thanks in advance