To keep the form factor small but offer heart rate monitoring for fitness purposes to those who want it, the CORE 2 will give consumers the option to purchase an accessory strap with an embedded heart rate sensor.

ENGADGET: BodyMedia's CORE 2 armband tracks your health, or lack thereof

In addition to simply tracking your total poundage, there will be bands for tracking heart rate and the S 4's various sensor can help judge the comfort level of your environment.

ENGADGET