I carried a T-Mobile BlackBerry 8800 with me on my last two trips, one of which involved a 90 minute limo ride from Monterey to San Jose. This ride gave me lots of time to contemplate what I could have done had I been on line, so once I got to the airport and hooked into the 'net (for some reason, it's free at SJC; it might have been a fluke of the day), I went hunting for experiences using BlackBerry 8800 as a Bluetooth Internet gateway for OS X.
I've been down this road before with Nokia phones, but back then, the best connection one could finagle with T-Mobile was GPRS at 9,600 bits per second. With the 8800, you can fish for hours and see a lot of wild guesses and tales of non-helpful interactions with T-Mobile tech support. Cut your search short: The instructions shown on the Fibble.org forum hit it right on the head. Just follow the instructions pointed to by the preceding link and you'll be on-line in a couple of minutes. You must follow them to the letter or you'll waste a lot of time.
The secret sauce is the modem script. The author has done an excellent job of equipping it to write connection status to Internet Connect's log window.
The T-Mobile plan you'll need to make a data connection is BlackBerry Unlimited. With that, the 8800 will hook to the Internet using the carrier's EDGE network. It's not remotely like 3G, but it's a kick compared to GPRS. I tested it several times and found that it averages 128 kilobits/second downstream and 31 kilobits/second up. Latency stinks. However, I was able to carry on real-time ssh sessions with the Xserve in my lab using the open source midpssh terminal. The menus are a bit fiddly, but once you get connected be sure to select "Type" from the menu to get an interactive session. Otherwise, you'll get an annoying buzz every time you press a key.

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