Name: Walk n'Play
Available for: iPhone
Cost: Free

Web sites:

http://www.cpl.uh.edu/index.php/projects/walk-n-play/
http://itunes.apple.com/bw/app/walk-n-p ... 07041?mt=8

Walk n'Play is a game app for the iPhone that aims to encourage people to exercise throughout the day. It uses readings from the iPhone's accelerometer to compute the number of calories expended while walking. The amount of calories a user expends is pitted against that of a friend or the simulator. At the end of the day, the one who has burnt the most calories wins. The idea is that a little bit of competition will encourage people to walk more.

It's a simple idea and the implementation is also simple. After downloading the app from the Apps Store, the user provides some simple data for the User Settings: username, name, age, height, weight, sex, avatar, and, if one wishes, Twitter login information. There is also a setting for specifying where the iPhone is on the body; this setting is important for the correct calculation of calories expended. The user then chooses either to play against the simulator or against a friend. Playing against the simulator is easy: one simply selects the simulator and then chooses the simulator level (light, moderate, high, and athletic). If one chooses to play against a friend, one goes to the Buddies section where one chooses a friend, either someone known to the user or someone unknown but in the same time zone. A request, which can be accepted or rejected, is then sent out to the friend. Whichever feature one uses - the simulator or a friend - the app keeps track of the calories burnt by both throughout the day. There is also an activity history feature that allows one to see, for the period of a month, the amount of calories expended each day. The app also has an option for sending texts to Twitter. If your have a Twitter account, you can manually or automatically send texts to update your exercise status. This could act as a further encouragement to walk more.

It should be noted that the app only claims that it keeps accurate track of calories expended while walking. It will record calories expended for other activities, such as jogging, running, or biking, but it makes no claim of accuracy for these figures. It also makes no claim of accuracy if the user does not specify correctly the position of the iPhone on his body.

I've been using this app for about two weeks, with the simulator, and I have found that it helps to encourage me to get up more which is the whole point. I have beat the simulator set on 'light activity' every day and will be changing it to 'moderate activity' for a new challenge. As I tend to carry the iPhone on me as I go about my daily activities, it doesn't get in my way and has not caused me to change anything but the amount of walking I do. I would say, therefore, that within its limited scope, the app is a success. Not bad for something that is free.

There are problems, however. First, the app is only available in English, and not only that, but just US English - it doesn't even support British English. Although I am a native English speaker, as I live in France, I prefer to work in French as much as possible to improve my language skills, so I find this lack more than a little irritating. Second, the number of avatars available is extremely limited: for the user, there are only two avatars, a male cartoon figure and a female; for the buddy or simulator, there are the same avatars as for the users and a vampire avatar. Given that one of the features touted as part of getting people to like - and therefore, use - the device is the fact that it has avatars, the lack of a wider choice is more than little puzzling.

The most important problem, though, is that the method for calculating calories is not specified anywhere easily available, not in the app's help, or on the app's web site. The web site says that the device correlates iPhone accelerometer values with virtual VO2 cardio-pulmonary instrument measurements: in other words, it correlates the iPhone measurements with a computer model. What is this model? The answer is probably in an article that appears in the Proceedings of the 2009 ACM Conference on Human Factors in Computing Systems (Y. Fujiki, P. Tsiamyrtzis, and I. Pavlidis 'Making sense of accelerometer measurements in pervasive physical activity applications', 4-9 April 2009, http://portal.acm.org/citation.cfm?id=1 ... N=43812385), but as this article costs 15 USdollars, I have not downloaded it. If those who devised this app wish to give users greater confidence in it, this information should be freely available.

Despite these problems, I have still found the app useful as a motivatial tool. It appeals to the competitive side of me and encourages me to do more so that I can win the race every day. If a small bit of competition is what you need, therefore, to get you up and moving more, if you have an iPhone, I recommend giving this app a try.