I was just looking at the same functionality for my site and I found a couple of resources.
But after reading up on these options, I think I'm going to go with what Ashley suggested and use the email-to-sms services. In my situation, I just need it for after-hours service notifications. Most of my company is on Sprint anyway, so that makes things pretty easy.
By the way, here's a good list of the various email-to-sms services by service provider.