David Kirchhoff, Weight Watchers' president and CEO announced yesterday that Weight Watchers will soon submit an iPhone application to Apple in an effort to provide "convenience and information on demand to further [members'] weight-loss success and to further modernize the Weight Watchers' brand."

Weight Watchers is one of the most recognizable brands in the consumer health industry, but do they need an iPhone app? As you might expect, nearly all of the most downloaded applications in the Health & Fitness category in the AppStore are nutrition, exercise and/or weight loss-related. The WW app would have to compete with the many free or cheap apps already popular among iPhone users. The Weight Watchers app will be a free offering, but only for current Weight Watchers members, which begs the question: How many Weight Watchers members have iPhones?

Since Weight Watchers' aim seems to be to provide a mobile offering for its existing members, as opposed to using an iPhone app as a means to attract new members (a free or cheap app available to any iPhone user would be the strategy there), the company would do well to consider a more horizontal approach to its mobile offering so all of its mobile phone-equipped members can take advantage of it. Why not offer a text message based service whereby members can text in the number of points they are consuming to their online database? Members could also text in their weight each time they step on the scale. Weight Watchers could, in turn, provide encouragement or reminders via text message to all its members.

If Weight Watchers is going to offer an app for its members, anyway, let's determine how that app could have the biggest impact, while sussing out what has made other weight watching apps popular to date.

The next big opportunity for iPhone app developers looking to tap the health and fitness market is the race to create applications that interact with medical peripheral devices via Bluetooth. Apple recently demonstrated a prototype of a Bluetooth-enabled glucometer developed by LifeScan that could send information to a corresponding app. Apple has announced plans to open up its Bluetooth API for medical devices, so applications that leverage this functionality will probably hit the market sometime next year.

Why doesn't Weight Watchers lead the charge with an application that automatically populates with a user's weight every time they step on their Bluet00th-enabled scale? The bigger brands need to step up their app development efforts if they want to compete with the health app incumbents, and Bluetooth-enabled devices might be just the ticket.

Continue reading below for a slideshow of the currently most downloaded iPhone applications that Weight Watchers' iPhone-equipped members are probably already using. Let us know how new entrants can distinguish their health and fitness apps or whether it's all been done before.

Top Paid Health & Fitness App: iFitness

True, Weight Watchers is typically known for its tracking of eating habits along with fluctuations in weight, however, the company's online offerings include tips for getting in shape as well as some instructions on how to correctly do certain recommended exercises. iFitness, the current top paid app in the Health & Fitness category is completely focused on helping users correctly perform certain exercises. iFitness costs the users a one-time fee of $1.99.