I know I shouldn’t do it, but I still ride my bike with a ear buds. No, it’s not the safest thing in the world, but I tend to be a risk-taker. Besides, the hills near my house are quite a challenge to climb on two wheels, so the right tunes give me that extra boost. Yamaha might not agree with my lack of safety, but I’m sure they agree about the extra boost the right tune can provide. That’s why they offer the BODiBEAT digital audio player.
This device monitors both your pulse with a wired ear-clip and your rate of speed with an accelerometer, using that information to dynamically match the music to your pace. If you change your pace often, this likely won’t appeal to you because the device will be constantly changing songs. However, most moderate to long-distance athletes tend to grind out mile after mile within mere seconds of the last. I seem to recall that’s how I did it in my prime, but I’m over the competitive hill now. ;) You can create custom training programs, use the preset BODiBEAT programs and even sync the device to a PC for your training stats. At $299 for a device with a meager 512 MB of flash memory and a passable 12 hours of battery life, it may sound pricey, but it could add tremendous value if you’re looking for that exercise boost.

Man, why would I want to hear dirges and other funereal music?
Or instead of spending money on a “special” device to match your music to your heart rate, you could just build smart playlists for your basic levels of workouts like is outlined in this blog post:
http://brentevans.blogspot.com/2007/06/make-itunes-workout-or-mood-playlist.html
BODiBEAT is intriguing. If you want your favorite artists’ songs on your player, already rated by BPM, check out jogtunes.com (http://jogtunes.com). The site has links to the iTunes Music Store where you can buy tunes for your player. Yamaha says in their promotion that the player accepts AAC file (iTunes files).