iKcon Infotech VOIP is a FREE SIP softphone application for voip calls over 3G or WiFi.
iKcon Infotech's key features include:
- Lowest battery usage with highest reliability / stability on google play
- Lowest latency of all android softphones
- Excellent audio quality, even on older devices
- Supports calling over 3G and WIFI
- Background / multitasking support
Speakerphone mute and hold
- UDP and TCP transports (use TCP for better battery life!)
- Supports g711 (ulaw, alaw), speex, iLBC and gsm codecs.