You could get a Blue tooth receiver. I just purchased the
OnCourse Blue tooth GPS Receiver Edition 3, which is on sale for $39.95. I love it allot. It's small enough to carry in my pocket and it has a nice soft feel.
There are plenty of other BT receivers available. From what I've read, any of the latest BT receivers are good. There are 2 different types of chip sets, Sirf III and MTK. MTK is rather new, but still good. You will see different channels for the receivers, from 10, 20, and even 51 (with MTK). This refers to how many satellites the receiver can access. Supposedly, any of the current receivers can access up to 10 receivers to work properly, so I'm unsure why MTK chip sets would offer 51 channels.
The software I use is
TomTom Navigator
. There's no subscription cost, but you need to buy the software. If you already have a GPS receiver, then just buy the software. Otherwise, they also sell bundled packages, which includes the software and receiver.
If you go with TomTom, you will need at least a 1Gb SD card, since you will have to install the maps on the SD. The main program can still be installed on the device. I currently use a 2Gb SD card, but since I keep my data, backups, and apps on the SD card, I order a 4GB sd card. Make sure you buy an SD card, NOT SDHC, which is SD HIgh Capicity. SDHC is NOT supported on the Treo 700wx.