EDIT: Sept. 5, 2009. The information presented in this post is possibly out of date. Specifically, the dial-up telephone number is suspected to have been suspended by T-Mobile UK. For information on how to use this same mobile as a GPRS-capable modem in Snow Leopard (Mac OS 10.6), please read this other post.
I've always liked the idea of being able to connect to the Internet from anywhere. I'm a PhD student after all, the Internet is my life now. The problem is when I'm not near a Wireless Hotspot or an Ethernet port. Cellular Signals are the next best thing: my mobile here in the U.K. has Bluetooth, my Powerbook G4 has Bluetooth. There should be a way to use my phone as a sort of modem for the laptop. Well, yes, apparently there is.
It took some time to figure out, not because it was difficult, but because T-Mobile (my carrier) doesn't give a lot of information for the appropriate setting to make this happen.
As it says on the title of this post, I used a Motorola L6 phone. My Powerbook G4 has Mac OS X 10.4.11 installed. No other software was needed.
First, I paired the phone with the laptop. It's a pretty straighforward process, I just needed to turn on Bluetooth on the Mac and on the phone and make it be discoverable. During such process though, it was important for the Mac to know that it can use the phone as a modem; almost at the end it asks such question. It can use the phone as a modem in two ways; the Motorola L6 and T-Mobile work with GPRS, so that option should be checked.
After that, it will ask for what script/driver to use and other information that T-Mobile for some reason doesn't make public, but I found them and I know for a fact that they work.
Script/Driver: Motorola iR TimePort (7089). (This one took a long while to uncover...)
Telephone Number: +447953968999
Account Name: user
Before you hit that "Connect" button, though, go to Systems Preferences, make it show the Bluetooth settings. Then, under the PPP tab, click on PPP Options and uncheck "Use TCP header compression". Apparently, it doesn't like it when the header is compressed, complains about it quite a lot in the logs to the point that it crashes the pppd process, leaving the device unreachable afterwards (something about failing to open the device file, because of permissions).
Also, be aware that even though I can now potentially connect to the Internet anywhere there is a cellular signal, it is very slow (took almost half a minute to pull up Google.com) and very costly (it is making a call after all) so, even though it's a nice choice for connectivity, it should just be a very nice last choice.