Can I view my calendar or input data to other applications while talking on the phone

From TreoCentral

Q: Can I view my calendar or input data to other applications while talking on the phone?

A: PalmOS Treos

Yes, you have complete access to all of your other applications (except those which use the serial library during a call, such as another wireless application). Therefore, you can view your calendar, enter an appointment, write a memo, create a to do item, take a photo, or enter contact information in your address book—all while talking on the phone. Of course, this feature is most useful when using the included headset or in speakerphone mode.

To access contacts press the phone button, this will take you to your normal phone screen, where you can search for contacts as normal. Pressing the Phone button again will take you back to the 'Call in Progress' screen.

You can do anything you would normally do on your Treo simply by coming out of the 'Call in Progress' screen. However, you may want to plug in a headset or put the Treo on speakerphone first!

A: Treo 700w/wx

Yes, you have complete access to all of your other applications, excepting those which require an active data connection, such as Internet Explorer. During your call, you may open up the Start menu to switch to another application.