Garmin released its Edge 500 head unit at around the same time as CycleOps released its Joule. Each of these was an ANT+ Sport compliant head unit which could read power data from compliant power meters like the Quarq and PowerTap. However, otherwise they almost couldn't be more different.
The Joule's focus was on functionality. Power users like to analyze their data, CycleOps reasoned, so we're going to give the user as many options as we can fit to crunch power numbers and even do history analysis. This sounded good, but the head unit is the wrong tool for this job. Riders would upload their data at the end of the ride anyway, for example with Golden Cheetah or WKO, then may be from there to a web site like Training Peaks. So the result was a heavy, bulky, and expensive head unit which sold like coldcakes.
And despite all the cost and complexity the unit lacked GPS. Why burden a head unit designed for a power meter with GPS? The Wattage List old-guarde eschewed GPS, and many still do. When I'm riding, all I care about are the hard numbers: speed, power, and altitude for context. I know where I rode, and frankly it doesn't matter much, they argued.
Garmin on the other hand scored huge with the 500. It focused on recording, not on display. And like all Garmin units it had GPS, of course. Sure, it told you what your present numbers were, but any sort of historical analysis was minimal and difficult to access. Even, for example, checking the power from previous intervals during an interval session required way more button clicks than anyone should attempt on-the-bike.
But in the San Francisco Bay area, the things have sold insanely well. I'll do group rides where 80% of the people have Garmin GPS units, most of them Edge 500. So why -- why do people need a GPS unit which barely even tells you where you are? Certainly my Edge has never helped me avoid getting lost or helped me find my way back from being lost. Although it does have limited navigational "follow a route" functionality, most users don't know how to use that. I've never seen noticed doing so. Frankly, most riders know where they're going; they don't need a GPS for that.
So if they don't need a GPS to tell them where they're going, why use a GPS? Around here, it seems to me the #1 reason is one that didn't exist at the time the Joule or Edge 500 were released: Strava. Strava is the paradigm shift in what Bike Snob calls "Cat 6 racing": competing with friends outside the domain of sanctioned events. It's also been called "asynchronous racing". Sure, this has always existed. People would obsess over their Old La Honda times, the records up that hill passed on in a complex oral tradition. But with Strava you finally have hard data accessible by all. And not just for Old La Honda, but for virtually every bump in the road. If you're not the Old La Honda KOM or QOM, there's surely some undiscovered hill somewhere where you can be KOM or QOM.
Power is hard to understand. Maximal power curves, smoothing functions, fourth-power norms, training stress scores... but speed is speed and everyone understands that point A to point B in the minimal time is what it's about.
Strava has been called the "social network for cyclists". It's been the killer app which has made a GPS unit essentially mandatory for the "competitive club riders" here, and it's catching on elsewhere as well.
So CycleOps responded with a the new Joule. Sleeker and lighter than the first Joule, this one has a GPS option. So clearly it's being recognized position determination on a bike is more than a passing fad. DC RainMaker has an initial review. So what's next?
I think the next thing is connectivity. Strava seems to be leading the way here with their phone apps: first for the iPhone, and upcoming for the Android. Since the phones are connected, data upload can be virtually real-time. The Android app promises to do one better: to provide near instant feedback on performance on segments, allowing a rider to know how they ranked on a just-completed climb even before they have time to catch their breath. There's obviously all sorts of possibilities once a computer is connected. For example, you can imagine being able to track other riders in your group.
But before getting carried away, I wish to return to the emphasis on relative simplicity in head units. Record + transmit. If I want to analyze data and run fancy apps, at least for now, leave that to the phones and other heavier, more power hungry, more general purpose devices which can be brought along if one wishes. Keep the cycling specific hardware light, robust, and simple. The key is to not keep the data sitting idle, and to not require users to perform cumbersome up-loads at the end of the ride. That should happen automatically, wherever you are, as long as you're within access to a wireless data network.
It'll be interesting to see more details on the Joule, but I'm even more interested in what Strava does wth its Android app.