Now and then a forum question is posted about iPhone tracking apps for bike touring. You know the deal: You want an online map to be updated with your location so friends and family back home can follow your progress.

For this type of thing I wrote an app called TrackMyTour. The app lets you update an online map as described above, but you must do it actively. In other words, you must manually add points whenever you want to highlight a location. This works well and keeps battery consumption at a minimum since the app isn't constantly monitoring your location. However, some people would like to do their tracking in a passive way (i.e., without manually entering anything).

Most passive trackers I've seen double as a cycle computer that monitors your speed, altitude, location, calories, and bunch of other things. They work in the background, but also consume a lot of battery since the app is constantly monitoring your location. This is great for short trips but impractical for bike touring.

In iOS 4.0 Apple introduced a feature for tracking "significant location changes" with the promise of consuming less power at the cost of accuracy. As far as I understand, this feature does not use satellite GPS and only generates updates whenever the phone switches from one cell tower to another (which is something your phone is doing anyway). For this reason it allows tracking with very little battery consumption. It also promises updates every ~500m, which is reasonable for touring.

Where am I going with this? I'm wondering if a tracking app that takes advantage of this feature would interest the bike touring community. Or does anyone know if such a tracking application already exists? The app would likely upload your movements (at a configureable frequency) to a server, where friends and family can follow along, or you can embed the data into your blog or website.

Anyway, if you have any thoughts or comments I'd like to hear it. Thanks.