While the Nike+ kit serves a means to an end for many runners, it may not suit everybody's needs. There's the additional cost of the transmitter and receiver (USD $30) for iPod nano owners -- iPhone and iPod touch owners need only purchase the transmitter for USD $19. Then there's the cost of Nike running shoes, which are the only shoes that accommodate the Nike+ transmitter; or as a workaround, you could get a pouch that fits the transmitter on your shoelace; and these usually run about $10.
And then there's the issue of accuracy. I personally find a calibrated Nike+ kit very accurate. For instance, during a 4 mile run (I mapped out the trail on walkjogrun.net prior to running) RunKeeper Pro showed that I ran 3.95 miles while Nike+ showed 3.90 miles. Others, however, have not been as fortunate. And this is understandable, as the kit works by detecting the steps a person takes; and as runners' gaits and strides can sometimes change during a run, this may affect the kit's accuracy.
Accuracy issues aside, RunKeeper Pro, at face value, appears little different than Nike+: at its core, RunKeeper Pro aims to track your running progress, albeit with different technology than Nike+. But dive a little deeper, and what you'll find is a training gem, especially for interval-based workouts.
What separates RunKeeper Pro from the basic version of RunKeeper (which is free) [iTunes link] as well as Nike+ is its ability to customize workouts. To demonstrate its customized training option, let's set up RunKeeper Pro for the Yasso 800 interval run. The Yasso 800 is an interval workout made famous by Runners World Chief Runner Bart Yasso. The goal is to align your goal marathon time with your Yasso 800 time. So, if your goal is to finish a marathon in 3 hours and 45 minutes, you'll need to do an 800 meter run in 3 minutes and 45 seconds, followed by a 3 minute and 45 second jog. The first week, you'll want to do 4 sets, and work your way up to 10 sets several weeks prior to a marathon.
Setting up intervals is relatively simple, and feels similar to creating an Automator workflow on the Mac. You're given the option to select between speed (slow, steady, and fast) and time (in 15 second increments) or distance (in quarter mile increments). To add more intervals, simply tap the "+" button.
One of the neat things about running with the iPhone is that it gives you the ability to open up your ears to a wider spectrum of listening sources. iPhone OS 3.0 introduced the capability to background stream audio, and many Internet radio streaming apps (such as WunderRadio [iTunes link] and ESPN Radio [iTunes link]) provide built-in support for this. So, if you're sick of personal music collection and want to surprise your ears, you can listen to BBC Radio 1 as you're 5,000 miles away running across the Golden Gate Bridge. All the while, apps like RunKeeper Pro will be tracking your running progress.
While GPS tracking gives RunKeeper an edge of differentiation over Nike+, the other edge of sword has at times provided minor annoyances. The nature of GPS is such that a clear line of sight is required for best results. To this end, I've found on many occasions that running under a bridge will disrupt tracking. In addition, when GPS signal is disrupted, in my tests I found that, while GPS tracking resumes as soon as a signal returns, audio cues did not work.
These minor annoyances aside, RunKeeper Pro serves as a nice alternative to Nike+, and it's also a great gift idea for the runner in your life!