You don't need a template really. Just take Apple's own Default.png and that essentially tells you where the buttons are. You can also use Loring's template (see the Downloads section):
http://www.modmyi.com/forums/downloa...do=file&id=242
And finally for a spiffier calculator version, check out my just released calculator version here:
http://www.modmyi.com/forums/downloa...do=file&id=242
Download it and you will see how to make a fancy calculator screen using your own background. Essentially, you create 4 files:
1. Default.png (this is the screen that is loaded as you launch calculator 320x460)
2. CalculatorBackground.png is the bottom portion of the calculator (320x371, just crop the Default.png accordingly; this screen is overlaid after a second or so when the calculator has loaded)
3. LCDBackground.png is the top portion of the screen (320x91. again crop the Default.png; this screen is also overlaid). Note that the Apple's original png only is 1 pixel wide and is scaled to take up the entire top portion (leaving little flexibility for fancy graphics). I tested larger versions (320x91) and they work.
4. ring.png is the highlight that is applied when the memory is filled and the math operators are pressed (53x53; needs to be largely transparent to see the buttons below). You can also change the size of this png if needed. Check out my calculator to see what kinda stuff you can do to highlight.