Originally Posted by BobbySteel

That's not truly end-to-end. It initiates a regular phone network call, then joins the calls based on your outbound call. So it still uses minutes technically. It feels end-to-end but it's hacky since it uses the phone network.

Sipdroid is 100% over wifi or 3G DATA only. Trust me. I use this daily in the UK w/o using any minutes whatsoever.