I just downloaded an application called SipPhone, $6.99. It allows to you an existing SIP account on your iPhone to make calls with Wifi. Similar to Skype (Which isn’t sip based) you can use a voip service like Vonage on your iPhone.

There are many VOIP providers Vonage. Voicestick, PhonePower, Callcentric, Gizmo5, etc. If you get this app and are connected to WiFi you will be able to make and receive calls. So if Vonage offers you free or discounted international calling this is an extension of home account.

I am currently using SipPhone with my Voicestick.com account. They have a “next to nothing plan” which is $2.99 a month and then 1.53 cents per minute to call the US.

There may be better VOIP/SIP accounts out there and I am curious as to what others are using. If you use something other than Vonage please post a comment here. At home I use PhonePower.com but they don’t offer SIP access.

If you travel international and want your home phone to ring on your iPhone this is one way to do it. As mentioned above it also allows you to make cheap or free phone calls depending on what VOIP provider you have.

To learn more about the app go here: http://www.vnet-corp.com/iphone.htm

Fring also does this but that is through a gateway vs direct connect so there can be latency issues.

The company is working on push notification so I think in the future it will mean the app can run in the background.