The icon must be simple, and clear, because it will only be viewed at small sizes on small (phone) screens. No text on the icon, please, because the icon is labeled at all times, so text is unnecessary.
Since the app is all about turning settings on and off, you may want to try to send a message of turning things on and off with your icon. This is merely a suggestion, and in no way a requirement. Please design the icon however you see fit.
** Most important requirement: **
The icon must conform to the Android Icon Guidelines at http://developer.android.com/guide/ (the Launcher icon section.) It's very important you follow these guidelines!
The icon can be in either vector or raster format, but if in raster format, it must be at least 1024x1024. AI or PSD, please.