Should be wifi
I like the idea but (1) it should send a broadcast (including your unique grill id) over wifi so that multiple people can receive the information over a wider area (150 ft, through walls also, is somewhat limiting for some houses), and (2) someone needs to investigate methods of using a Peltier generator running off of the temperature differential between the grill and the surrounding air (possibly meaning the device wouldn't need batteries at all). I know this last part is reaching, but the wifi is definitely doable. Just think about Eye-Fi cards.
I like the idea but (1) it should send a broadcast (including your unique grill id) over wifi so that multiple people can receive the information over a wider area (150 ft, through walls also, is somewhat limiting for some houses), and (2) someone needs to investigate methods of using a Peltier generator running off of the temperature differential between the grill and the surrounding air (possibly meaning the device wouldn't need batteries at all). I know this last part is reaching, but the wifi is definitely doable. Just think about Eye-Fi cards.