When it first come out, the world went a bit crazy over Wii Fit and its included accessory, the "Balance Board". A few years on though, and how many people still use the software, let alone the hardware? If you'd like to put the gaming gadget back to work without having to fire up your console, you should check out FitScales.
Available via Google Play for the always-excellent price of free, FitScales allows you to sync your Bluetooth-enabled Android phone with the Balance Board and use it like a regular set of scales. The app also supports syncing with FitBit and RunKeeper, if you happen to use them.
Unfortunately, due to an undocumented API change in Android 4.2, the app only works on devices running previous versions of Google's mobile OS.
On the bright side, FitScales is open source -- you can grab the code from GitHub if you'd like to take a peek at how it works, or even make your own modifications.