Now you can hook up your jailbroken iPhone to Bluetooth keyboards and type your heart content through the Bluetooth Keyboard Driver which is a part of Cydia on all iDevices with Bluetooth support. Based on the open-source BTstack project, the app is available in Cydia as "Demo" and works inside the app itself.
Once you start the Keyboard demo, you need to make your Bluetooth Keyboard discoverable and enter a PIN when you get a pin code alert. Then you will get connected and you can then use the keyboard to type into the text field. You can also use the Home‚Äù button to go back to the Springboard and enjoy the keyboard support in other applications.
Visit ModYouri for more detailed steps.