I’ve played around with a number of iPhone apps for cyclists. None of the ones I’ve looked at are really optimized for bike touring—instead, they’re mostly oriented towards fitness cycling, which has somewhat different goals.

An iPhone app for bike touring would need to overcome the problem of battery life and fulfill three main tasks. Battery life isn’t as big a problem as it is generally made out to be, but even in a best-case scenario, it would be difficult to get a solid 24 hours of use out on a single charge when using the iPhone as a bike computer for a big part of the day.

1. Show you where you’ve been

This is what most cycling apps already do, so it’s the least interesting thing to discuss. They sample your location frequently (every second or two) using GPS and create a track based on this data. This lets you derive a lot of useful information—speed, distance, altitude, etc.

It’s not clear to me how much this frequent GPS sampling drains the battery. I found while riding the Southern Tier that I could get up to 10 hours of continuous recording with Cyclemeter if I turned off all the other battery-draining features. A bike tourist probably doesn’t need such frequent sampling. For the purposes of show-and-tell, every 10 or 30 seconds might suffice. Though I can imagine that the battery savings from this might be minimal.

Infrequent sampling would not be useful for showing speed, since one’s course could twist and turn enough over a 30-second interval that straight-line connections between points would be inaccurate. Speed isn’t all that important to a bike tourist, but falls into the nice-to-know category. An iPhone receiver for ANT+ (a standard protocol for wheel-rotation and heart-rate sensors) recently hit the market. Again, it’s not clear to me whether infrequent GPS sampling plus an ANT+ receiver would beat frequent GPS sampling in terms of battery life. Having wheel-rotation data would be useful as a check on occasional GPS freakouts.

2. Show where you are

Again, this is pretty much a solved problem with the default map app on the iPhone. For a bike tourist, it could be useful to know what services are nearby for food, water, shelter, etc, so a map view customized to pop up this kind of information by default would be helpful.

A bigger problem is viewing the map. It is not practical to keep the screen lit all the time. A number of cycling apps deal with this problem by relying on spoken updates rather than a visual interface as the primary way of getting information to the rider, but again, this is oriented towards fitness cyclists. Better would be for the backlight to turn itself off and allow the rider to turn it on briefly with a tap on the screen.

3. Show where you’re going

This is related to the problem of showing where you are, and is where the most work remains to be done.

There are plenty of apps that will plot a route between two points, but these are generally oriented towards motorists. Google Maps recently added bike routes, and Mapquest is also working on bike routes. Which is nice, but many bike tourists are following meticulously planned maps rather than routes calculated on the fly. And while these maps may exist in the form of KML files, getting them into an iPhone and displaying them in a useful fashion is a problem. There aren’t many apps on the iPhone that allow one to import and display a KML file at all, and the ones that I looked at are little help: the KML files for the Adventure Cycling Association’s route maps involve thousands of waypoints that overwhelm these apps.

Even assuming the problem of importing complex KML files were solved, the problem of showing the route to the rider would remain. Showing a line on the map isn’t difficult, but again, it’s not practical to keep the screen lit all the time. I can imagine lighting up the screen only when a turn is coming up, perhaps accompanied by a sound to get the rider’s attention (and perhaps another sound when the rider goes off-route). While there’s nothing technically impossible about this idea, Apple will not permit apps to control the screen backlight directly, so Apple would need to change its rules for something like this to work.

4. Communicate

This is a semi-solved problem. Many cycling apps can send periodic updates by e-mail/Twitter/Facebook automatically, and I took advantage of this while riding the Southern Tier so that Gwen would get regular status reports. Getting the actual GPX track out of the phone and doing something useful with it is more of a mixed bag. I was able to figure out a roundabout workflow for posting my daily reports to my blog that worked, but it could have been easier.

Cycling apps seem to have been going through a burst of creativity lately, and I’m optimistic that a good touring-specific app might see the light of day. A protective handlebar mount that included a backup battery would complete the package.