It TALKS? What do you mean it talks?
Yeah well - some of it does. Indicating silica gel starts out as one color such as deep cobalt blue or yellow and then turns to another color. When the product begins to adsorb moisture, blue indicating silica gel, for example, will turn pink and yellow silica gel will turn green. This lets you know it's time to replace or regenerate the product.
A simple pH reaction with some specially added ingredients allows these silica gels to actually let you know when they're used up and needs to be replaced.