I don't know since when, but now Nimbuzz supports G.729! Finally, there is an acceptable VO3G - Voice Over 3G, my terminology. Next to it is Acrobits 2.00 and old, offering quite acceptable VO3G.
Interestingly, G.729 is still not listed in the Nimbuzz app, only three options are there: auto, G711 and iLBC. iLBC is the very best codec for VO3G, but few VOIP providers support this great codec. The trick is to chose "auto", then Nimbuzz will use G.729 when iLBC is not available. Nimbuzz won't use G711 when it sees the current connection is 3G.
It is a little tricky to show your phone's contacts in Nimbuzz. You have to check "load phone numbers" in settings and give a phone # to Nimuzz, a fake one will be accepted. Then, go to the contacts tag, display group, select all contacts or phone numbers only.
Skype uses iLBC, but it drains battery too quickly and there is no free DID. Acrobits 3.10 and later also support iLBC and has battery-drain problem too: it keeps phone awake all the time, draining out battery within several hours. Strange, 2.00 and older do not have this problem.
Nimbuzz connects to SipSorcery and SipGate fine, but CallCentric won't allow apps like this and Fring to connect. This is too bad, because CC now offers free DID (see my other article). There are some NAT handling issues between SipSorcery and Nimbuzz: when you use WiFi, i.e., behind NAT; the other end won't hear you although you can still hear him/her. No problem between SipGate and Nimbuzz, and SG does support iLBC!
So, the best VO3G solution is Nimbuzz + SipGate. Second to that is Acrobits + CallCentric. As always, for flexibility, you should integrate them with GoogleVoice and SipSorcery or freeSWITCH. I'll write an article about how to set them up.
To download Nimbuzz, open your phone's browser to: