Battery Go! is a simple, but useful application for the iPhone and iPod Touch that gives you critical information about your battery life. It does its job well, but for a paid app I'd expect a bit more.

The main page displays your device's current battery percentage with a 5% margin of error. The developer openly announces that the application should only be used as an estimate. Based on your current battery percentage the app will display how much time you have left to surf the web, use the phone, listen to music and watch video. So, maybe you're on plane and would like to watch a movie, but the app tells you that your battery will die half way through the movie. Now, with that information, maybe you'll listen to some music instead so you have enough battery life to use your phone in case of an emergency. The app can really come in handy to help make some important decisions about how you'll use your iPhone or iPod Touch.

The main screen also includes a slider to help with some hypothetical situations. You can slide it to a higher percentage than you currently have to see what level of charge is necessary to get the time you need for specific activities.

The only other part of the app is an extra page that shows some battery saving tips, some of which you probably never knew about it. But, the app doesn't really offer anything else, which is a bit disappointing for a paid application. I honestly don't know what else you could add to a battery percentage application. It would be nice if the app could sense other applications that your device is using. For example, maybe the app could tell you that your bluetooth is on, and if you turn it off you will gain a certain amount of battery life. What if you could ask the app to tell you what to turn off to gain an extra hour of talk time? Maybe some of these features will be in the next update.

Yes, Battery Go! is useful, but it's not something I'd use on a daily basis. Is it worth a buck? I'm not so sure, but that's up to you.