The Battery Master app is an upgrade to Battery Master free. The only real difference I see in the Free and Pro app is that there are more application choices. Battery Master Pro is a productivity app that shows you how much battery you have, and how long you can continue to use certain applications before the battery on your iPhone or iPod touch dies.
The only thing I don't like about this app is that the times may not always be accurate. You can set the "battey capacity" of your device, since times are only estimated. But most of the time, I find the battery life times to be accurate.
Overall, I find this app to be extremely useful, and I use it almost everyday, especially when I am on-the-go and not near a charger.
Below is a screenshot from the app:
|Screenshot - Battery Master|
Here is the link to purchase Batter Master Pro for $0.99: http://itunes.apple.com/us/app/battery-master-pro/id326647737?mt=8&uo=4
Or download Battery Master Free for free: http://itunes.apple.com/us/app/battery-master-free/id326819555?mt=8&uo=4
Thanks for reading!