Metronomes have been used for centuries to establish tempo and help musicians practise.
These days, digital metronomes are also available.
There are also virtual metronomes accessible on the internet.

Here are some free web metronomes (some are downloadable):


Software programs such as Garage Band and Audacity allow the user set the tempo and create loops and music pieces.
Audacity is downloadable free from:

iPhone & iPod
Metronome apps are downloadable for iPhones, iPads and iPods
Just search for metronome in your App Store.