Meld is certainly interesting; manufacturing is going to be a challenge for them with a lot of moving parts, but in any case, it may work for some soups/stews types of dishes, but it won't be compatible with most of Pantelligent recipes (asparagus, eggs, crepes, pancakes, bacon). And a Meld-style internal temperature probe alone would be significantly worse than Pantelligent for foods like steak and salmon; I know that at first glance it seems like internal temperature is the temperature to measure and optimize for, but you also have to control the external/surface temperature or else it's "unobservable" and will lead to either undercooked or overcooked meats! You can not simply do feedback around the internal temperature. (That's one of the key engineering insights of Pantelligent.)
A few years ago I wrote an app called Sous Vide Dash that was initially targeted at professional level kitchens-and later white labeled by PolyScience, the leading provider of professional sous vide equipment. We did full thermodynamic simulation in that app, and modeled both temperature and pasteurization. To my knowledge it's still the only cooking app that has an embedded numerical solver for partial differential equations. In 2012 we won the StarChefs International Chefs Congress Innovator award for our work.
Popping back to the top of the stack, it's a very exciting time for precision cooking. As one of the founders of Meld, I can tell you there is a lot more to come.
To me, it looks the most compelling because it's both the cheapest and most versatile.
I backed both Pantelligent & Meld. But if Meld would have kickstarted first, I wouldn't have backed Pantelligent.