The MotionX-GPS for iPhone is a great GPS and very accurate, with or without a cell / data signal. I've been using a Garmin eTrex Vista C for 4 years, but it's just one more piece of equipment to carry. And since I almost always have my iPhone when I'm skiing, hiking, or biking, having a GPS on my phone seemed too good to be true. But it's not.

One of the best things about the MotionX-GPS is that it allows you to have a real GPS application on your iPhone.

The following are some of the MotionX features:

• Loads free topo maps in real time . If you have a data signal, you can download free topo maps.
• Preload free topo maps . If you know you will not have a data signal, you can preload maps. I mountain bike and cover a lot of terrain, so I downloaded 100 square miles of maps at two zoom levels. Now I can see detailed and high-level maps even when I have no data signal.
• Surprisingly good battery life . I have done several 20 mile rides, 3-5 hours each, with tracking turned on for the whole ride, and the battery made it. In most cases, the battery was almost dead when I finished the ride, but the complete GPS track was recorded. I think the Garmin battery life is about the same. Unfortunately, you can't change batteries on the iPhone, so if you are serious about tracking your route on long rides or hikes, you should look into a solar charger with battery pack for the iPhone.
• Trip data : longitude, latitude, altitude, total ascent, distance, speed.
• Share Track Data . This is where the MotionXGPS really shines. Like most GPS devices, the MotionX allows you to track your route. Once you save a track, you can instantly share it via email, Facebook, or Twitter. No longer do I have to export the data from my GPS into a mapping program and then export it from the mapping program into an image file, blah, blah, blah. Just click share and your done. Now for the good part. The shared file contains most of the data from your track.
• A link to Google Maps. Just click the link and it displays your route on a topo map on Google maps. The great thing about this is you can share your route with anyone. They don't need any special software to view your route.
• A.gpx file. You can import.gpx file into a GPS or mapping program and view the route
• A.kmz file. If you have Google Earth installed, you can double-click the.kmz file to see your route on Google Earth.
• Attach an image. You can attach any image on your phone or take a new image. When you share the file, the image is attached to the email. Furthermore, if you click the track in Google Maps, it displays the track data AND the image.

The MotionX-GPS is a great iPhone app, but it isn't perfect.

• If I have the MotionX sounds turned on, the application is EXTREMELY slow. To fix this, I turned off the sound. (this is on iPhone 3G. Not sure if the same problem exists on newer models)
• When you create a track, you get a lot of data, but one of the most important to me is the total ascent. Unfortunately, when I share the track file, it does not include the total ascent, only min / max altitude.
• On the free topo maps, the complete area of ​​Grand Teton National Park is shown in blue, as if it were a lake. I assume this is not the only area where the map data is bad. I hope they fix this soon since I spend a LOT of time in this area.
• Battery Life. This is not really a MotionX issue, but if you plan to use this app and your iPhone to replace a dedicated GPS, you will need to solve this issue. Most likely, you will need a solar charger / battery pack for the iPhone to extend the battery life.