I'm using the Uniden GPS device. The antenna portion sits on the dash of my vehicle and does a pretty good job.
Serial GPS Receiver for Scanner and Marine Products
In the past I've used a Garmin eTrex Legend with a 12 volt power wire. It did the job but I didn't like leaving an obvious GPS device on my dash for security reasons.
Any NMEA compatible GPS device works as long as it has that 9 pin RS 232 connection.
(The antenna you posted is but part of a system commonly found on public safety vehicles and buses. It connects to another "box" inside the vehicle. The primary use for that setup is to communicate the vehicle's location to a dispatch center computer so the closest resources are dispatched as needed. This is called "AVL/GPS" or automatic vehicle location based on global positioning system.)
Using a GPS device for location based scanning is a very handy feature which I believe you will like.