I find it incredibly simple and handy to send application alerts (and sometimes friendly notes) via email to an SMS-enabled phone. Most of the big carriers have an email to SMS gateway. Here are the email addresses of the top 6 carriers.

T-Mobile

phonenumber@tmomail.net

Virgin Mobile

phonenumber@vmobl.com

AT&T

phonenumber@mmode.com

Sprint

phonenumber@messaging.sprintpcs.com

Verizon

phonenumber@vtext.com

Nextel

phonenumber@messaging.nextel.com