best voip software for iphone?

[tsx]

i've been looking around, have the config file from fpl for my home and more than happy with it.
would now add the voip functionality on my iphone when i am not home throught a hotspot.
only concern is that it seems like that this setup when i get home will "screw up' my home config since fpl doesnt work on multiple devices at the same place...
(ie need to reset/ unplug my home ata...)
is that true?
if so how would you recommmend to use it and which voip would you suggest?
i've seen siphon, isip, acrobits, fring... so many, dont know which one to try.. any recommendation?

thanks in advance,

[laurent]

Yes. Both SIP devices will steal the registration from one another. Depending how fast they renew their registrations, you may have several minutes of availability before the other one grabs it.

Either:
1. You disable your home ATA when you leave and re-enable it when you get back.
2. You use FPL's followme feature to simply forward your phone to your cell while you're away.
3. You get a different SIP account to connect your cellphone with, and then use a switching service to connect them together, like pbxes.org for example.

About clients, fring and nimbuzz don't work with DTMF. Siphon works very well (but only the RC version from google code. The one in cydia is old and has codec issues.) I don't know how well Acrobits works, but people have said good tihngs about it. However, it's not free.

[tsx]

Yes. Both SIP devices will steal the registration from one another. Depending how fast they renew their registrations, you may have several minutes of availability before the other one grabs it.

Either:
1. You disable your home ATA when you leave and re-enable it when you get back.

so you mean that the sip devices will not only compete when i am at home but also when i have wifi on my cell phone away from my home?
so its either sip on the ata at home or on the go with the iphone but never both at the same time even if not at the same location?

[laurent]

That's correct. SIP was built to handle one device to one server. If you want multiple devices, then the next step is not provided by FreePhoneLine. There are services like pbxes.org that try to fill this niche. They can provide you with multiple SIP accounts to their service, one for each of your devices, and then connect them all up to one or several SIP voice provider (such as FreePhoneLine).

With such a setup, each phone device is independently managed by a server, and all those accounts tied to a phone line. You can have, as a result, all phones ring at the same time when there's an incoming calls. In a sense, this is what Google Voice does with phone lines. We can do it with VoIP as well.