This is an intriguing concept. If you’ve got Outlook 2007 and the right wireless service provider (Verizon and Sprint/Nextel out here in California right now — you can look up whether your providers handles this from this link), you can have Outlook send you text messages (SMS) with reminders of events, tasks and even important email.
Note that I said “Outlook”, not your Exchange server. It appears that you need to leave Outlook up all the time to make this work. Oh, did I forget to say that you need a Windows Live id, too? From what I’ve read (SMS Link main page here and FAQ here), the trigger even occurs and Outlook connects to a service that Microsoft provides to send the SMS. You can also supposedly send arbitrary text messages from Outlook as well. Since my provider’s not signed up yet, I can’t test this out but if you can, please let me know how it works for you.