I use a Kyocera 6035, which covers me for my phone, pager, and palm. It's killer for when I'm out and need to shell into a server to restart a service, or to check mrtg graphs to monitor traffic. The service I'm with is Alltel.com and they have what they call speachless messaging, which is basically 2way text messaging between phones, email, there's even a webpage people can send me messages. The nice thing about it is, it doesn't use up my cell phone time
It's like $6.95/mn and I get unlimited incoming and outgoing messages. So I have my PC setup to email me stats every hour during the day so I can keep and eye on all the servers. Anyone that has both a phone and a pager should look at switching, and the palm pilot is just an added bonus, I never thought I would use the address book and the calender that much, but I'm totally hooked now, I use it to keep everything.
Tim