Oh, Sand Trap, Where Art Thou? G.P.S. units are increasingly geared to specific sports.

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 Tibur�n 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.

3. Bushnell ONIX 400
Price: $500
For boaters, the Bushnell ONIX 400 shows standard and nautical measurements. It's unaffected by stormy weather but does a good job predicting it. The handset picks up 178 channels of XM Satellite Radio, including NavWeather, which delivers local reports on a color screen, just like an evening-news forecast. A minor design issue: The exposed metal ports may corrode in salty air.

4. Garmin Rino 530HCx
Price: $536
The Rino includes an altimeter, a speedometer, and a two-way radio with a range of up to 14 miles. Others carrying devices on the frequency show up as blips on the color screen, making it easier to meet fellow skiers mid-mountain. (It also lets you know when to head home; the radio picks up NOAA weather channels.) One caveat: The Rino is bulky.

5. GolfLogix G.P.S.
Price: $350, plus $30 annual subscription
Because hole positions on a golf course often change, GolfLogix (which has hardware made by Garmin) gives measurements to the front, center, and back of a green. A yearly $30 subscription fee lets golfers download an unlimited number of course maps from a library of more than 15,000 worldwide. The cell-phone-size handset can store up to 10 course maps at a time.

Find a Friend
G.P.S. tools for the socially inclined

In addition to sports, G.P.S. receivers are also playing a role in social networking. "About 20 percent of our users choose to be public," says Jason Uechi, co-founder of Mologogo, a G.P.S. application for cell phones that tells your friends-or if you opt to be "public," anyone who visits Mologogo.com-where you are at any moment. At Montclair State University, for $215 a semester, geeks and nongeeks alike can carry Sprint phones equipped with Rave Wireless, a similar, phone-based G.P.S. technology. And endurance athlete Dean Karnazes, who ran 50 marathons in 50 states over 50 days in 2006, uses Bones in Motion, another mobile-phone G.P.S. program, to promote his memoir, Ultramarathon Man. It gives his location to fans and is accurate to within three feet. "People show up at random street corners and run with me," he says.