Three-dimensional representations of buildings are also starting to appear -- but although the necessary map data is widely available, devices with the memory capacity to hold it are not, according to a spokesman from Horizon Navigation. The maps require over 2G bytes of memory, which is the limit in many devices on the market, he said. The company demonstrated Version 4 of its NavMate software, which will soon be released. Horizon is looking for device manufacturers to adopt it.

GPS devices aren't all about the display, however: some are designed not to be seen. That's the case with the Locator from Portuguese company Inosat Consultoria Informatica. It has a battery life of up to 30 days, the company said, and transmits its location periodically, allowing you to track your "loved ones" via a Web site, Inosat said. Other companies exhibiting similar new products from Laipac Technology of Canada and Algodue of Italy. Algodue also makes waterproof trackers if your loved one is a keen swimmer.

One expensive asset that many would like to track is the second Galileo satellite, Giove B, the launch of which has been delayed to next month. Galileo is a European Union project to complement the US-owned GPS : Using signals from the GPS and Galileo satellite constellations together should make navigation devices more accurate. Swiss company U-blox tried to demonstrate its chips capable of receiving signals from both constellations, but show-goers had to wait patiently for Giove A, launched in 2005, to pass overhead to see the Galileo part of the demonstration. Giove A orbits about once every 14 hours, and is visible for only a few hours at a stretch.

One of the most intriguing gadgets discussed at the show was Garmin's Nuvifon, a tiny touch-sensitive tablet that is both phone and navigation device. It will display driving routes and let you surf the Internet or type text messages using an on-screen qwerty keyboard -- although not all at the same time, Garmin said. The company only had nonfunctioning mock-ups on display at its stand -- the same size and weight as a working product, a representative helpfully said -- so it will be a while before this one is ready to challenge the iPhone. Garmin hopes the Nuvifon will find its way to market in the third quarter.

(With additional reporting by Jeremy Kirk and Nick Barber in Hanover.)