Like Google Voice, MagicJack's app works on any Android device which means you don't need a mobile phone plan for it to work just a wi-fi connection to be able to make calls and texts. MagicJack is also available for iOS devices. Unlike Google Voice MagicJack users do not have the ability to send or receive MMS. I personally have never used the service and don't plan on using it, however it does appear to review well in each respective app store.
Although MagicJack is not an MVNO, BestMVNO does from time to time discuss free calling apps to supplement many of the MVNOs that have talk and text allotments that do not include unlimited calling and texting such as the $30 T-Mobile plan that I use which only includes 100 minutes of talk.
Do any BestMVNO site visitors out there use MagicJack? If so what do you think of it, and have you compared it to Google Voice?