[Change 5060 to 5062 or 5061, if you want more codec support than G729]
Once installed, open it, click menu, settings, SIP Account Line 1:
Authorization Username: your line # such as 12345678831
Password: the password for this line
Server or Proxy: sip.kots.us
Check the networks you use, such as 3G
Once everything went well, you'll see a green dot on the left top corner and you are ready to call.
Forward your ipkall or Callcentric DID to port 5080 (not 5082) if you use G729 as the preferred codec.
If call volume is low, adjust the levels in Audio/Video.
There is a 5-year-old bug in Sipdroid that causes registration loss after a while especially after a network change. And you should add G729 to it if you use it over 3G. Voice may be garbled when use G729. I have fixed all these bugs in Sipdroid source code.
See how little battery drain with Sipdroid on KoT VOIP, plus two gmail accounts sync and WeChat, only 4% drain after 10 hours and still has 76% left after 24 hours:
Nimbuzz is battery friendly and it supports G729. Configuration is very simple: press the menu key, Settings, Call Settings, Set VoIP provider, SIP Provider, Other VoIP account, and fill in your line number, password and domain like this:
You may add port after the domain, e.g., sip.kots.us:5061. Other softphones such as x-Lite are very similar.