I purchased both Polyscience Sous Vide Toolbox and Sous Vide Dash on the same day thinking they might be different. Anyone who thinks theyre not functionally identical is misinformed. The ONLY differences are the colors and the selection of circulators. Polyscience Sous Vide Toolbox even refers to itself as "Sous Vide Dash" within the app. PSVT allows you to select from a wider range of Polyscience circulators than SVD and unlike SVD does not allow selection of other brands of equipment (though it does include "Generic Non-circulating" and "Generic Circulating").
This is a useful tool for estimating time-to-temperature for various thicknesses and shapes of food and for estimating reduction in 3 pathogens (E. Coli, Listeria sp., and Salmonella sp.) Its flexible and has fairly reasonable defaults, and includes a fairly wide range of specific foods so you can select lamb loin chops vs. rib chops instead of just going by shape and size.
My recommendation is to buy Polyscience Sous Vide Toolbox if you have a Polyscience circulator or like red, or buy Sous Vide Dash if you have a different brand of equipment or like yellow. One or the other is certainly worthwhile if you plan to cook anything sous vide.