G.P.S. receivers were once reserved for helping soldiers navigate the battlefield. Then the service was extended to directionally challenged drivers. Now, a host of new devices uses the constellation of 31 global-positioning satellites to help amateur athletes choose between a nine iron and a pitching wedge, track their performance on the slopes, or go running in unfamiliar cities map-free.

Deer Valley Resort in Park City, Utah, offers SlopeTracker, a G.P.S.-enabled armband that costs $35 a day and gives skiers a map that traces their movement on the mountain, along with their average and top speeds, vertical feet traveled, and calories burned. G.P.S. units are also showing up at golf courses around the country. Each cart at Tiburón Golf Club in Naples, Florida, comes equipped with a 10.4-inch screen made by GPS Industries. (Greg Norman is a principal investor.) Golfers playing courses that don't have G.P.S.-enabled carts can choose from a range of handhelds that detail thousands of course layouts on proprietary maps.

Below, five new devices that offer competitive advantages for their respective sports.

1. Timex Ironman Trail Runner Bodylink
Price: $350
Timex's watch-size Ironman includes a digital heart-rate monitor and an option for setting up to 10 waypoints, which can guide lost runners back to their starting positions. Serious athletes will probably wish that Timex would simplify the device by doing away with the armband that holds the G.P.S. 3-D sensor. You'll need a separate device to download training data to a computer.

2. Suunto X9i
Price: $549
Suunto calls the X9i a wrist-top computer. Good for hunters, it has a compass and an altimeter to assist with tracking and a barometer and graphs to help gauge weather patterns. A USB hookup allows for route viewing on Google Earth. The downside? The device's huge face makes it incredibly dorky for everyday use.