I use my pda which syncs via bluetooth or infared at computers at work, so i can always be online with my servers. There is an emergency email that customers can email incase of major problems (downed server, etc), which sends an SMS to all my tech's cell phones.. works out pretty good.
We have it setup with our Datacenter for $25 a month if a service (HTTPD, FTP, SSH, Etc) goes down or if there is an important message it is automatically forwarded to myself and a partners cell phone via text message. Normally I have a laptop sitting in the back seat of my car.... So as long as someone has a phone line or broadband I can get online rather fast.
I use a mobile phone/cell to check for new emails when Im away and I also provide SMS support for business accounts.
I can get access to a computer most of the time anyway but its good while Im out to check if I have got a new support ticket/email