## 3 Results  
A comprehensive literature review was conducted to examine the major technological trends and developments that are reshaping pet care in smart scenarios using the IoT. The findings provide definitive answers to the five research questions (RQs). RQ1. What Are the Types of IoT Devices/Prototypes Most Used for Pet Care and What Functionalities Do They Offer? 3.1.1. IoT Devices Proposed at Academic and Research Level  
The literature review revealed the existence of various prototypes focused on the care of different types of pets. Prototypes focused primarily on the care of dogs (e.g., S9, S10, S18, S19, S20, S30, S33, S34, S35, S47, S57, S68, S69, S71, and S75), cats (e.g., S12, S15, S17, S21, S25, S29, S38, S41, S49, S51, S56, S72, S78, and S81), and even both (e.g., S3, S8, S13, S16, S24, and S29). However, it was also evident that IoT prototypes for the care of fish (e.g., S1, S58, S76, and S79), chickens (e.g., S44), turtles (e.g., S26 and S53), and rodents such as hamsters, rats, and hedgehogs (e.g., S11) have been proposed. Additionally, there were prototypes focused on the care of pets in general, without specifying a target segment (e.g., S2, S4, S5, S6, S7, S11, S13, S14, S22, S23, S24, S27, S28, S29, S31, S32, S36, S37, S39, S40, S42, S43, S45, S46, S48, S50, S52, S54, S55, S59, S60, S61, S62, S63, S64, S65, S66, S67, S70, S73, S74, S77, and S80). The prototypes developed by the authors of the analyzed studies were presented at different levels of detail. Some presented their preliminary ideas through sketches (e.g., S22), while others were limited to presenting the circuit diagram of the prototype (e.g., S3, S8, S14, S24, and S31). However, most illustrated the prototype from a real-world perspective (e.g., S1, S2, S4, S5, S7, S9, S10, S12, S13, S16, S18-S23, S25-S30, and S32-S81), showing them implemented on the actual pets used in the experiments. It is also important to note that some researchers did not present the prototype itself, but rather limited themselves to describing the software application or directly presenting the results (e.g., S6, S11, S15, and S17). Figure 5 presents 49 IoT device prototypes designed for pet care. The majority are automated food and water dispensers for dogs (18.5%), cats (17.3%), or both (7.4%), and for general pets (53.1%). Notably, prototypes S1 and S29 are specialized for fish feeding. This prevalence of feeding devices indicates a focus on home pets, particularly cats and dogs, which are the most popular pets today. The prototypes previously illustrated in Figure 5 have the common goal of allowing owners to provide food and water to their pets. The IoT allows them to perform this action automatically when they detect the presence of the animal or, alternatively, to do it manually but remotely, i.e., from their work or wherever they are physically located. This ensures that the animal has food and does not die from malnutrition, or that the food is portioned to avoid diseases such as obesity or diabetes (e.g., S8, S9, S13, S30, S34, S49, S55, S59, S61, S72, and S78), a very common clinical conditionin pets today, especially in those in which there is sedentary lifestyle due to being locked up in apartments or houses. Proper portioning must be based on factors such as the pet's species, breed, size, physical activity level, and veterinary-recommended diet. To ensure a healthy and adequate diet for pets, various technological proposals have been developed. However, some of these proposals do not conduct a rigorous evaluation of the precision of the portions they dispense. For instance, studies S8, S13, S34, and S78 lack comprehensive assessments of the portioning accuracy. Study S55 introduces a device designed to regulate pets' eating habits and train them for scheduled meals, but its effectiveness remains unevaluated. Similarly, S9 only claims to provide optimal feeding without presenting detailed performance metrics. Conversely, other studies have evaluated the effectiveness of their devices to varying degrees of complexity.