I recently had someone ask about sending video download links to mobile phones. Mux does this using the “your phone number”@”your mobile carrier”.com approach, otherwise known as the SMTP Email Gateways.
Every carrier has a different way to do this, with different limitations, but it does essentially work, and as long as you aren’t spamming people, it is a good solution.
Here is a mostly complete list of the gateways from SMS411.net