I use google voice and use the number for work. I love it.
You can cut the cord assuming wifi. You'll need the app and you can get voicemail and text messages on the number...the voicemail will have be translated to text in your email. I just don't understand how its feasible to always be on wifi to make this worthwhile.
You want to give it a test spin, if you have an old cell phone download the app and try it.