UPDATE: Nintendo's latest accessory will be paired with DS game Personal Trainer: Walking. http://www.nintendoworldreport.com/newsArt.cfm?artid=16838 Apparently Nintendo has been hard at work developing brand new hardware for consumers to take advantage of. A recent filing with the OHIM (official European Union agency responsible for registering trademarks and designs) reveals that Nintendo has created a pedometer, likely for use with Wii.
Becoming more popular in today's health-oriented culture, pedometers are a simple tool that tracks the amount of steps a person takes. Given the health applications of the tool, a Wii Fit sequel seems to be a likely fit for it, though nothing is officially known about the tool or its applications.
Given the fact that the pedometer itself has no external display, it seems unlikely that it will function as a standalone product and will likely need to interact with some other software in order to retrieve the information the pedometer stores.
UPDATE: It's not WiiFit that the pedometer is intended for, but the recently revealed DS game Personal Trainer: Walking. The pedometer made an appearance in a DS highlights video that Nintendo presented at their Japanese Fall Media Summit. It will interact with the Personal Trainer: Walking software, keeping track of the user's walking activity during their daily activities.