Add-on GPS units were among the earliest and sexiest accessories for PDAs. A GPS could help you find out where you were and track your progress on trips, using the PDA's display and software downloaded from a host PC. But adding GPS capability typically requires a bulky add-on or a CompactFlash card.

Now Garmin, one of the most respected names in the GPS industry, has entered the PDA market with an intriguing convergent device, the Garmin iQue 3600 ($590 street). While the Palm OS 5.0–based iQue 3600 isn't inexpensive compared with many conventional PDAs, it's cheaper than buying a PDA and a GPS add-on.

The iQue 3600 has 32MB of RAM for map data and other Palm applications. Conveniently, an SD card slot lets you save map files (which can be large) separately. The 6.6-ounce device has a 2.2- by 3.2-inch 320-by-480 backlit 16-bit color display.

The GPS unit itself is a WAAS-enabled, 12-parallel-channel receiver with rated GPS positional accuracy within 15 meters and rated WAAS accuracy within 3 meters. The GPS antenna fits into and folds out from the top of the back of the case. Close it and it turns off, conserving battery power. If you're going to use the iQue in your car for long trips, it's probably a good idea to buy the optional 12-volt car power adapter ($30 direct).

The iQue includes a vibrating alarm and an MP3 player function, but its primary function is as a location and navigation device. Bundled software includes Garmin's GPS clock, address lookup, mapping, tracking, trip computer, router generator, and turn-by-turn voice guidance programs. On our tests in the Hartford and New Haven, Connecticut, areas, the iQue 3600 performed as well as any add-on GPS unit we've tested.

During installation a base map of major cities, roads, and state and county boundaries is loaded on the PDA. A license is included to use detailed map and POI data from a two-disc MapSource City Select.

The iQue's applications use moving maps; just move the cursor to any edge and the map moves to the next area. You can also easily zoom in or out for more or less detail. We tested routing to locations in the Hartford area, and the software quickly showed us the best way to get to our favorite pizza places.

Integration with the Palm address book is helpful: Tapping the "Route to" button automatically generates a route to any address on your contact list. And the mapping feature quickly shows you how to get to the next appointment on your calendar.

If you often travel in new areas, Garmin's iQue 3600 is a handy single-device combination. Use it as a regular PDA when you're not out and about, but when you need directional help, flip up the back panel with confidence.