ContactsBook is a useful address book application.
You can easily organize contacts using tab and drag & drop and send message to group members.

-#2 top paid app in Japan
-#1 top paid Utility app in Japan

Group management
There are functions to;
-create, edit and delete a group.
-select group icon.
-create group icon from photo or text.
-order group tabs.

Contacts management
There are functions to;
-create, edit and delete a contact.
-call a contact.
-send eMail or SMS/MMS to a contact.
-classify a contact using drag and drop to group.
-classify multiple contacts using drag and drop in edit mode.
-order contacts using drag and drop.
-sort contacts by name, organization name, color, creation date and birthday.

Messaging
There are functions to;
-send eMail to group members.
-send text message to group members.