Yamaha launched the Bodibeat awhile back.
It's an MP3 player that calculates the BPMs of the songs in your library and monitors your pulse while exercising. Then, it tries to play faster songs when your heart is beating faster.
Here's a short, but vague, video that puts this into context.
In theory, this could be totally awesome.
In application, I know there have been some complaints that the Bodibeat doesn't hold as many songs as an Ipod. (It's got 512MB--which is enough for a few workouts and not much more).
Also, while it was a big hit in Japan, Yamaha is no longer making them in the States. I talked to the rep at Yamaha, who said that Amazon picked up the last of their inventory--and when they're gone, they're gone.
So, if you want to read more about it or pick up one of the last few, you can find them here:
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