In a world of gadgets, computers, and Smart Phones, bbq gadgets were inevitable. I'm not convinced that these gadgets make you a better cook. I see them as a convenience item. If you can't cook, these gadgets aren't going to help you too much.
Some of these gadgets I've seen cost more than the cookers they are used on (example: older WSMs like mine).
I see the bbq gadgets as an excuse to buy another toy. I like gadgets myself with two laptops and two Smart Phones in our household. I doubt I'll ever buy one for any of my bbq cookers. I prefer to buy cookers that don't need such elaborate temperature control. My WSM will cook all night without a computer and I sleep like a baby.