I have been using VoIP services with my wireless phone for years. My first VoIP service was with Bellsouth Mobility the “One number service” which was provided by Call Sciences. I was able to have my cell number ring 5 different phones at the same time or it could ring one at a time until I was found. I could listen to my voicemails online and forward the message to anyone. One of my favorite features was being able to put someone on hold and call someone else speak to them then combine those two calls by themselves. When I answered the phone from my land line I would not use any of my cellular minutes.This service was truly ahead of its time.
These days I use Google Voice which gives almost all the same features as I had with the One number service and Google Voice has some different features like on my contact page of my Blog you can click the Google Voice icon and call me. Google Voice also transcribes my voicemails into text and emails and or texts them to me. The application on my phone gives me the visual voicemail feature that you see on iPhones or you can get from YouMail. I also use Google Voive
Kineto’s Smart VoIP Goes Head To Head With Google Voice, Skype | PCWorld Business Center
eVoice(R) Launches New VoIP Mobile App for Android(R) – MarketWatch