There are a bunch of apps on iOS and Android that let you TXT Message other people only using a Wi-Fi internet Connection. I've used What's App on both iOS and Android which works great. I've heard great things about TextNow. And you may know that GroupMe was purchased by Skype which was purchased by Microsoft. Are there any good solutions for Windows Phone?

I'd prefer a solution that allows actual SMS/MMS Texting and not a 3rd party solution/client as I find them to be less reliable.