Great question — answering as the UphillTech team:
It turns out this is 100% possible, though a little hacky. If you want it to work on Android you need to use this format: <a href="sms:/* phone number here */?body=/* body text here */">Link</a> If you want it to work on iOS, you need this: <a href="sms:/* phone number here */;body=/* body text here */">Link</a> Live demo here: http://bradorego.com/test/sms.html (note the "Phone and ?body" and "Phone and ;body" should autofill both the to: field and the body text. View the source for more info) UPDATE: Apparently iOS8 had to go and change things on us, so thanks to some of the other commenters/responders, there's a new style for iOS: <a href="sms:/* phone number here */&body=/* body text...
Full answer by Brad Orego: https://stackoverflow.stackexchange.com/a/19126326 (CC BY-SA 3.0).
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