The New Balance headphones and heart rate monitor combo will provide you with just that along with audio capabilities too. Apparently it works by giving the headphones a nice, firm touch, which would provide the device enough information to read your heart rate, at which point it would be presented to you in audio form through the headphones.
Compared to the other heart rate monitor options out there, which require a strap to your chest and a watch that displays your heart rate, I guess this is a slightly more convenient way to get your heart rate read while running or doing your work out, without you having to look down at a watch. No word on pricing but it is said to be available this summer.