fring™ uses your mobile internet connection to make peer-to-peer VoIP calls, send instant messages and talk with VoIP applications such as Skype, Google Talk , MSN Messenger and SIP at no extra cost.
D. Kumar, Y. Ryu, and H. Jang. CommunicabilityMS '08: Proceeding of the 1st ACM international workshop on Communicability design and evaluation in cultural and ecological multimedia system, page 39--44. New York, NY, USA, ACM, (2008)