Palo Alto, Calif.-based imo.im has announced that their popular instant messaging client now includes free voice calling for iOS users. Originally available only for Android devices, this new service allows customers to make voice calls to contacts using the free imo instant messenger app through Wi-Fi, and 3G/4G connections.

Originally released for iPhone in December 2009, the app allows users to chat with friends via Facebook Chat, Google Talk, Skype, MSN, ICQ/AIM, Yahoo, Jabber, Hyves, VKontakte, Myspace, and Steam. To date, 700,000 people use the service worldwide on a daily basis, with 50 million messages going out each day.

With imo instant messenger 3.2, VoIP calling has arrived for the first time.

Says Ralph Harik, CEO of imo:

At imo, our mission has always been to provide one place for family and friends to stay connected and maintain their close relationships no matter where they are located. The availability of free voice calling for iPhone users is a critical development for users looking to keep those valuable lines of communication open while saving on their mobile costs.

The imo instant messenger app is available for download in the App Store.