While looking for some voip softwares for my android mobile, I came across Octro (or Octrotalk). Its a multi platform mobile voip application founded by Octro Inc. The company was founded in 2006 with a mission to create productivity applications for Mobile Devices. Octro has corporate office in Cupertino, California and an offshore development facility in Delhi, India.
OctroTalk is a Jabber/XMPP/GoogleTalk client. It supports audio calling to your Jabber or Google Talk contacts. OctroTalk also supports calling to phone numbers using a SIP provider of your choice.