How to make certain apps turn on GPS automatically? Is there any way to have certain apps automatically turn on GPS when they launch (or at least prompt me if I want to)?

For example, if I use voice commands to ask for navigation directions, and GPS is not turned on, I'd like for it to enable GPS instead of guessing from cell towers.  Bonus points if it turns it back off when I close the app.
Take a look at Tasker.  It pretty much allows you to automate and set rules for everything on your phone based on times of the day, what apps you are using, your location...  You can set a profile to automatically turn your GPS on or off based on almost any condition you can imagine.