Why clutter up your house with a real metronome when you can use your trusty DS to achieve the same effect? Thanks to the homebrew community's continuing effort to turn the DS into the Swiss army knife of portable devices, soon, we anticipate the DS will be able to do just about anything ... and official releases offer a lot of practical options, too.
DSMetronome is the product of Demented, who noticed a hole in the system's abilties and filled it in tremendous fashion, building a clean application with built-in help. It may be simple, but DSMetronome does exactly what it's supposed to do, and does it well. Some games have included metronomes, but if that's all you need or want, this app may work well for you.