As mentioned in the comments, there are already plenty of apps that do this. I use JuiceDefender (Wifi on/off is the only thing based on location but it has pow

As mentioned in the comments, there are already plenty of apps that do this. I use JuiceDefender (Wifi on/off is the only thing based on location but it has power source/battery level/time related features too) but Locale and Tasker will do much more based on more triggers like mute ringer based on device orientation. A long time ago I thought how cool would it be if my Palm could HotSync over bluetooth automatically based on location (time was easy to do) but 3G and Google Calendar/Contacts have made that irrelevant.