It is possible to connect your Axim to your cell phone and access the Internet. If your Verizon account has Express Network (which it should, as it comes for free on most) you can get speeds up to 144k. Be aware, this will chew up your minutes. Unlimited nights and wekends are nice.
You will need to get a cable to connect the two devices. Check out
www.thesupplynet.com and
www.gomadic.com . I am not sure about availability with the X3i, however I know they have them for the X5. You will be looking at about $40.00 from gomadic, and $50.00 from thesupplynet. $10 bucks more, but it has a car charger that works for both devices.
Since you have the X3i, it's too bad you can't get a cell phone with a built-in Wi-Fi Access Point. It would be nice to be truly wireless. I wanted to get a Bluetooth enabled phone, but Verizon didn't offer one. Either way, the cost of a Bluetooth card would be similar to cost of the cable, and with the cable you can at least charge the battery.
Although.....
Axim X3i....$350.
Bluetooth enabled cell phone....$200.
Bluetooth card.....$50.
Being totally wireless.... priceless. :)