Whistle Phone 1.5

Whistle Phone brings free inbound and outbound calling in the contiguous US to your Mac. We also offer international calling at low rates.

Features Make and take calls from your desktop or mark yourself as unavailable Choose your look and feel from seven different skins Has built-in integration with your Mac's Address Book Includes two-line calling features, including call waiting and three-way calling Forwards your Whistle calls to any phone number via our Follow Me service Utilizes Apple's Bonjour technology to automatically discover and call Whistle users on your WiFi network Integrates with Growl for customizable missed-call notifications
And, one note: Your best experience is going to be with headphones. Using the built-in speakers and mic at the same time may cause echo.
Note: This application contains in-app and/or external module purchases.