Question: * So far, [Siphon](http://code.google.com/p/siphon/) is the best [SIP](http://en.wikipedia.org/wiki/Session_Initiation_Protocol) app I've tried.
* [MobileVOIP](http://itunes.apple.com/us/app/mobilevoip/id362528311) and [TruPhone](http://www.truphone.com/iphone) are very nice too (and don't need jailbreaking).
* Other apps offer at least some SIP features such as Nimbuzz, Fring, Viber and even Skype.
* Apple's FaceTime audio clearly is an option for some

While I have all of these, I hardly use any of them, for a variety of reasons.

I'm looking for a more ideal third party app that should:

* Integrate with both Address Book and the iPhone's native recent calls
* Replace phone.app and load rapidly to place phone calls
* Have [international number support](https://apple.stackexchange.com/questions/5223/using-international-phone-numbers-on-iphone)
* Allow [call recording](https://apple.stackexchange.com/questions/731/is-an-iphone-call-recorder-theoretically-possible/)

As a plus, 
- Support Skype, Google (talk, voice, etc) and integrate with other options if possible

Answer: 
After some problems getting DTMF to work I tried [WeePhone](https://itunes.apple.com/us/app/weephone-sip/id301500729?mt=8) with some success.
Prefer Sipgo. It's probably the app with the lowest bandwidth usage. No useless extras, just sip calls.