FastMail.FM now gives you the ability to send SMS (text) messages from your account to mobile phones. You can send messages from the Compose screen just by adding an address of the form <mobile -number>@sms (eg 447912123123@sms), or you can setup a forwarding rule to notify you when important emails arrive in your account.

Please see this FAQ page for more detailed information about the usage, limitations and pricing of this service.