Note: Tested only on Macintosh
If you ever run a performance while having your laptop on Battery, or if you have ever had your power cord get ripped out during something massive, then you might be interested in Huge Battery Status. It’s basically an indicator that you can put in your Extras folder or into max-startup. [...]

Download TapNTune 1.3 (9.3 mb dmg)
The all-in-one rehearsal tool for musicians.
“This tool is really great,  it’s simple and it does what is needed. I just love it!!!”
- User Review, Jnote.org
“There are very few metronome applications/widgets for Mac, and most have been disappointing. TapNTune is different: it works well, does what you want, and does it well.”
-User [...]

Note: This program may cause your computer to sleep during use: most notably during printing. For best results, disable it when not in use.  
A common problem with the Energy Saver preference pane in 10.5 is the failure of the Sleep option.  You can set the sliders to an amount of time after which inactivity [...]