[daveedem]

Make sure you update your device to the latest ROM and then you can use something like TomTom 6.

Then in your device.

Start | Settings | System tab:
1) External GPS = COM 4 [under Programs tab]
2) Hardware = None | Baud Rate = 4800 [under Hardware port tab]
3) Access = UN-check the "Manage GPS automatically [under Access tab]
The launch TomTom, Change Preferences, Show GPS Status, Configure, Scoll to the "Other Bluetooth GPS" option then tap on "Select" button, "Continue" button, Choose the com you just set and you are all set.

Until the latest ROM from HTC, I had to use Astro Launcher.. with the new Rom I don't.

hope this helps.