From time to time in the past, you’ve come up with all manner of excuses to skip a gym workout.

Your grandparents’ anniversary. The Shawshank Redemption on TNT. It’s Monday.

And, of course, the old standby: “I don’t have an easy way to time my interval training workouts on my phone.”

Sorry, that one is now gone.

Presenting the Bit Timer, a new app for your iPhone or iPad that makes timing your workouts in the gym a lot easier and more accurate, available now.

Picture it: you’re in the gym, ready to unleash some P180X-style fury (it’s like P90X, only double the intensity). You’ll pull up this app and establish the length of your workout and rest intervals (anywhere from five seconds to two minutes). Then, you’re all set.

You’ll start working out (with, say, Bulgarian split-squats). When the workout portion is over, your iPhone or iPad will sound an alarm and switch colors, telling you it’s time to rest. When rest time is over, you’ll hear a different tone and see a different color.

And don’t worry about not noticing the alarms over your music—the app momentarily fades out your playlist so you can hear the interval tones.

It’s hard enough to turn off Olivia Newton-John, let alone while exercising.