Best messaging app to group message iOS users?

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http://forums.androidcentral.com – Here's the deal. Pretty much everyone I text with any sort of regularity has an iPhone. They will frequently include me in their group messages, not realizing how confusing/frustrating it is to be getting random texts from 6 people at once, not knowing if replying to one of them lets them all see it, etc. So, what I'm looking for is a third party SMS/MMS app that will allow me to initiate group messages, receive group messages, and keep all group conversations grouped instead of separating them out to individual threads. Thoughts? What I'm not looking for: 1. Suggesting I get them (HowTos)