There are virtually hundreds of free and low-cost metronomes available for iOS, Android, Mac and PC. Here are just a few.
Free virtual metronome for Window users. Also available for iPhone.
If you own a Mac, this download may be the right thing for you. It works with OS X and got good reviews.
Mobile Metronome is a free metronome for Android users. According to its marketers, “it is easy to use, robust and has everything any musician can ask from a metronome”. Available on Google Play.
Another Android app. Fully functional metronome. Available on Google Play. Free and paid versions.
A BPM detector allows you to view the Beats Per Minute (or tempo) of a song. This can be useful for programming, for putting together running playlists or DJ mixes. Also useful for discovering a tempo and sticking to it. Some will analyze music on their own. Others allow you to detect the BPM by tapping or shaking your device in time with the rhythm that you hear. Many versions out there.
My favorite was an iPhone/iPod app called TapThat by Brian Flanagan. We can only hope that he brings it back some time soon.
BeatMe BPM Counter
This is an iPhone/iPod app that allows you to determine the BPM by tapping or shaking your device in rhythm. Available through iTunes Store.
Tuner apps are rapidly replacing the standalone electronic tuners of years past. Frequently free or inexpensive, the market keeps changing. Check iTunes, Google Play and the Mac App store for sources.
RK Chromatic Tuner
12 tone chromatic tuner. Listens while you tune and gives visual feedback. Inexpensive. Does what it says.