YOUNGSTOWN, Ohio - There are tens of thousands of health and fitness apps for iPhone and Droid users.

If you want to check your heart rate, there's an app for that. If you want to track your workouts, there's an app for that, too.

"It actually shows me how to hold the weights, how to do the legs, and how much to squat down," said Maria Lyras of Campbell.

Apps can even interface with cardio equipment. You still have to do the exercise, but the Nike Plus app will do the rest of the work for you.

"It's tracking your calories, your average heart rate, and then it's uploading all of that information right into the already built in app with your iPod or iPhone," explained Alison Straub, President of NTense Workout in Poland.

According to one mobile market research group, 500 million smartphone users will be using a health care application by 2015.

Some are better than others.

"People are out to make a buck and they don't always have the consumer and the patient's safety in mind," said Dr. Michael Gugliotti.

That's why the Food and Drug Administration wants to regulate some apps, including those that "are used as an accessory to a medical device that's already regulated by the FDA." An example of that would be an app that allows doctors to view x-rays and MRIs with the intention to make diagnoses.

The FDA is expected to release its official guidelines by 2012. In the meantime, doctors say there's a simple way for consumers to weed out the bad apps.

"They want to look and make sure there's nothing being sold to them or being marketed to them," said Dr. Gugliotti.

Fitness experts say people also have to be smart about they way they use apps, especially calorie counting apps.

"You definitely don't want to over train with them," said Straub.  "You just want to make sure that it it's something that you're compatible with, that it's asking you the correct information, like your age weight because that's what's going to help make sure that you're doing everything correctly."