I am part of a couple of groups that use SMS (sent from an email list server) for notifications.
Sometimes it works great, sometimes they are delayed 30min, 1hr,
Its amazing the phone companies can charge so much and offer so little.
Another issue with SMS "paging" is that phones are often not set up for that. By default, they're usually set up to be more discreet. They will often play a notification ONCE when the SMS comes in, and if you miss it, don't wake up, etc., you're screwed, especially if you're the only point of contact. A real pager will usually be much more persistent, which is important for heavy sleepers like me.