[headcanon]

In addition to having to know the carrier, the text message itself sometimes includes email-style metadata (like FROM, SUBJECT, MESSAGE, etc) that varies by carrier, so its difficult to control the experience. Its one of those things thats good for a personal project but not for a service that sends lots of text messages to users.

I didn't know this until I just tried it, but doing it over email supports replies (at least on AT&T), which is pretty cool.

[intrasight]

In the app I had built (for NBA) I think we just asked people for their carrier name. Or we may have used a lookup service - I don't recall.