App-loving fitness buffs now have a new one to try: MedHelp has partnered with GE to create a new free iPhone app, Fit Friendzy, which enables users to invite their friends to compete in fitness challenges.

Announced on July 5, the new app offers 50 challenges of varying difficulties, ranging from walking 30 minutes a day to completing a marathon to doing 50 pushups a day. You can track statistics of your routines and training, including distance, speed, calories burned, all while comparing them to your friends' results.

This is yet another app added to MedHelp's offerings, in addition to MoodyMe, which helps you keep tabs on your mood and emotional health, and I'm Expecting, an app for moms to be.

App users can also create an account on MedHelp's website, where they can wirelessly sync their data to MedHelp's online exercise tracker. Users can then share their data with their doctors, ask questions to doctors affiliated with the site, or get help from other users in the MedHelp online community.

Other fitness apps with a social element include Vivecoach, a mobile social gaming service that inspires healthy competition between you and coworkers by offering up fitness, weight-loss, or nutrition challenges, to see how you measure up to your colleagues.

Also, Runkeeper, the app to track runs for users, is now aiming to become a full-fledged fitness social network with the release of its Health Graph API that lets developers tap into its data and community, now 6 million users strong. Health Graph integrates fitness sensor data, such as GPS trackers, wifi body scales, sleep-monitoring devices, and heart-rate transmitters, with diet, workout schedules, social activity, and more to help users track and understand their health and fitness choices in a correlated way. The idea is to be a one-stop location for health data, all continuously updated from third-party gadgets, websites, and apps.

Download Fit Friendzy: