Have 2 iPhone lines on same account using unlimited plan. Recently found the relatively new messaging app and installed it on my wi-fi tablet. Was overjoyed that it performed as advertized and I could text to both apple and other phones at the same time through wi-fi. Problem started when I tried to install the app on my wife's 4G ipad and could not get past authentication. Initially tried all the tricks suggested by level 1 support to no avail. Finally had a system trouble ticket initiated. Assume someone in the tier 2 support was able to get something going because next day it sort of worked. But I had to uninstall to see I could get full functionality. Big mistake. Several more calls to support are not yielding any results, just pass the buck because there is not an established script to deal with application problems. Anyone else having trouble with more than one wi-fi tablet trying to use this application?