Any VOIP service that gives you an inbound number that you can forward your home phone to.
But you will need a jailbroken iPhone and a jailbreak/background VOIP app, or wait for the release of the 4.0 OS and updates to VOIP apps if you want to be able to receive an inbound VOIP call.
You COULD do this now without jail-breaking, but you would have to run the VOIP app all the time, which would probably make battery life suck. You'd still get inbound local calls, though they'd interrupt any in-progress VOIP call.
But why not just forward your home calls to your overseas local number? It's cheap enough with the right calling plan on your home phone or a third-party service. (e.g. your home phone forwards to a local or at least U.S. # that automatically forwards to your overseas #). Many VOIP and "virtual office" services have this option. That is, you get an inbound number in whatever area code you'd like, and then you can program it to automatically forward all calls to a number of your choosing. You pay their VOIP service's low rates for the forwarding from your home area code to your overseas number.
In most of the rest of world (non-U.S.) incoming cell calls are free, so you won't run-up a big bill on your local SIM. However, there will be a surcharge added by your VOIP service for terminating the call at a cellular number. You will normally see calling rates to Europe quoted separately for land or cell destinations. This is because of the European "caller pays" system.
