I bought the Qualcomm/Kyocera "Palm connectivity kit", which includes a data cable, a nice leather case to hold the phone and the PDA, and some browser and email software. It cost $100 from http://kyocera-wireless.com.
I have a handspring Visor and a Qualcomm 1960 phone, so I reverse engineered the cable and modified it to work with the Visor. Here is a partial schematic of the Qualcomm to Palm Pilot cable, as well as the (much simpler) schematic for the Qualcomm to Visor cable.
The new cable attaches to the Visor Hot Sync connector. These connectors are available at http://www.atllink.com for $2.66 each.
To get this to work, you must disable RTS/CTS flow control, set the baud rate to 19200. I'm not sure if you need to set the modem country to "other" - I had to do that when I used an external modem thru the HotSync cradle.
BTW, The leather case is very nice, but $100 for what amounts to a serial cable is outrageous. If I knew where to buy blank Qualcomm phone connectors, the whole cable wouldn't cost more than $10 to make.
You also need to get some software for your PDA, such as a Web
browser and a WAP browser.
I use these: