You may be a master griller, but I'm sure you can still find ways to up your game. One of these apps might help.: 10 Greats Apps for Grill Lovers from Mademan.com.
The GrillTime app is really cool. It tells you exactly how long to have to leave a piece of meat on depending on how you want it cooked. It also gives you times for sides like asparagus, potatoes, etc.
If you're into propane and propane accessories...
... check out the Propane Pro app. You hit your key against the tank and the app listens to the noise and determines how much gas you have left. You don't want to run out of gas at your big BBQ.