There’s no better feeling than having a successful workout at the gym, one where you push your body to its limits. You can take satisfaction in knowing that you hit that 100th crunch, or ran five miles around the track without stopping short. But quantifying how hard you worked can be difficult. That’s where Under Armour’s Armour39 comes in.

Armour39 is a performance monitoring system that plugs into a chest strap wrapped around your body. The device provides updates on your heart rate, calories burned and other biometric info, turning all of the data into a WILLpower score—a number between 1 and 10 that gauges your level of exertion. WILLpower takes into account the duration of your workout and your level of intensity, along with your gender, age, weight, max heart rate and more. Your WILLpower score and the rest of your workout data are available in real-time through a downloadable Armour39 app on your phone or watch.

During your workout, the chest strap keeps a firm without jiggling. It’s made of a material that wicks away sweat. The device itself holds a charge for nine months, so no worries about checking the battery.

So if you want to find out exactly how much effort you’re putting in at the gym, strap on the Armour39 and get moving. Bonus: It makes you look like Iron Man, and who doesn’t want that? You can buy the Armour39 module and strap for $150 over at Under Armour’s website.