I am ornery when it comes to mobile technology, so I might have been skeptical about giving running app PaceDJ a try. Then, the first time I used it, I ran 30 seconds per mile faster than my average pace for my daily run.Maybe, I thought, this technology thing isn't so bad.PaceDJ uses beats-per-minute data to compile a playlist that matches your workout pace. First, it walks you through a setup process that prompts you to identify your workout (choices include running, walking or biking) and effort level (easy, moderate or fast). The app then recommends a BPM range (if you want to go faster or slower, it's simple to adjust) and pulls music at the appropriate tempo from your existing music library.PaceDJ also has a Web site that offers pre-programmed playlists geared toward a goal workout pace. The site provides links to purchase individual songs or full playlists on iTunes or Amazon, as well as an option to listen on Spotify. I don't spend much time or money on iTunes, so I'm not really the target audience for this feature. But I can see the appeal of purchasing a music collection organized into a workout-friendly tempo.Another slick feature in PaceDJ (available only in the iPhone version of the app) is the ability to correct BPM data by tapping out a beat to a song. The slow, meandering "Della Brown" by Queensrÿche was listed at 154 BPM and repeatedly queued up when I was running with the app set for a moderate 155 BPM pace. When I tapped out the beat to the song on my phone, it corrected to 135 BPM. This is a fun feature. (Play the drums on your phone!) But who wants to stop and do this mid-run, when a slower-than-advertised song has delivered a buzzkill? Not me.There were a few downsides, depending on your level of patience. I noticed that songs tend to repeat. PaceDJ's customer service recommended a setting change to resolve that (set the BPM Shifting Range to Wide). Though the app offers distance/speed tracking, it requires enabling Location Services, and it didn't work on the Lite version of the app. A "Measure Your Pace" function did not work the five times I attempted to use it. On the upside, the full version of the app offers three standard interval workouts.After using the app for a few weeks, my average pace edged back to normal, though that probably had more to do with hilly, 5:30 a.m. runs than the uptempo music I was listening to. All in all, it was an interesting diversion from the relatively limited Shuffle playlist that usually accompanies me.