Locale basically lets you take actions on your phone, like changing ringtone volume, Wi-Fi settings, screen brightness, etc., when certain conditions are met, like when you arrive at a location, or if the battery is low, etc. The beauty of this is that they can be combined in any way. For example, I have it set up so that at work, my ringtone automatically changes to vibrate, so I don't bother everyone else with my phone calls. It also shuts off my Wi-Fi and Bluetooth to save battery power since I never use them at work anyway. Finally, thanks to Locale's plugins (downloadable from the Marketplace, some free, some paid), I change my Google Talk status to let everyone know that I probably won't respond to them because I'm at work. When I get home, the ringtone volume goes up, my Wi-Fi turns on and connects to my network, and my Google Talk status changes back. Oh, and since I hate putting in my security pattern all the time, I shut it off when I get home so I just have to swipe to unlock my phone. When I leave my house, the unlock pattern goes back on. When the battery goes below 30%, my phone goes into lockdown. I turn off my Wi-Fi, my GPS and Bluetooth to conserve that last bit of power. Then when my phone gets to 10% I turn the display down to minimum brightness as a last ditch effort. But all this is done automatically by Locale, after the initial setup, I don't even have to think about it, and I have definitely noticed an improvement in my battery time. Setup is pretty straightforward, you just create "Situations", which consist of a condition and a setting to change. Conditions are what cause the setting to change, so if you want your phone to vibrate when you're at work instead of ring, you would click on the GPS condition. This brings up a map, and you can tap your workplace and it's set. Then, in the Settings, just tap on the ringtone volume setting and push it down to zero. The uses for this app go far beyond what I mentioned here. Well worth the $10 for me. Highly recommended!