Is there a general consensus on the best texting app for a WiFi-only iPad? We have one at work and would like to use it to send SMS (and more importantly, MMS) but not all of the recipients will have iMessage. Whatever we end up with, it has to be able to send to mobile numbers, send pictures, and NOT require that the receiving person uses the same app. Should I just be looking at Google Voice, or are there other solutions (Text+, Text Free, Text Now, etc) with advantages of their own?