You can use the optional add-on "Handy Address Book Google Sync" to synchronize your contacts in Handy Address Book with your Google account contacts.  You can then sync from your Google account to a variety of phones, including the iPhone, Blackberry, Windows, etc.  (more info).  You can then make a change to your contacts on your phone, web, or in Handy, and keep all platforms updated.

To get started syncing, download and install Handy Address Book with Google Sync.  From within Handy Address Book specify your desired syncing options under the File/Options.../Sync dialog.  The sync options allow automatic syncing every so many minutes, or you can initiate a sync at any time using the Actions/Sync with Google menu command.

Specific Syncing Details:

The majority of the contact fields are synced between Handy Address Book and your Google account, but not all fields are synced.  Fields that are not synced remain un-changed.  The following fields are synchronized:

Name

Company

Job Title

Department

Emails:

    Home

    Work

    Other

Addresses:

    Home

    Work

    Other

Phones:

    Home

    Work

    Mobile

    Home Fax

    Work Fax

    Pager

    Other    (Handy's "Car" phone)

    Google Voice    (Handy's "Home 2" phone)

    Main    (Handy's "Business 2" phone)

Notes

Groups (Categories)

AIM

ICQ

In addition to syncing your contact information, Group information is also synchronized.  In Handy, these are your Categories, and on Google they are called Groups.  Your Handy categories will be synchronized with your Google Groups.  If you want to delete or rename a category (group), you must do so on both Google and Handy.  If you only want to add a category (group) you may do so on either platform, and that category (group) will be created on the other platform for you.