Body temperature monitoring, which plays a pivotal role in diagnosing the physiological state of an animal, depends on the methods used and their applicability within the production systems. Recent research has examined several methods, such as rectal probes, intra-vaginal radio transmitters, data loggers, reticular boluses, digital rectal, and microchip transponder thermometry RFID tags, for detecting body temperature in several locations, including the skin surface, vagina, subcutis, and rumen. However, the potential for device loss and the potential for stress induction are the drawbacks to these approaches. In this report, we propose, for the first time, the use of an innovative infrared (IR) photodiode thermometer to detect the temperature of cattle in real-time. Totally, seventy-five adult cows (Red Sindhi Cross (n = 25), Holstein Fresian (HF) Cross (n = 25), and kangayam (n = 25)), with an average age of (43.0 ± 0.4) months and a weight of 487.0 kg ± 42.5 kg, were monitored for 30 days. The surface temperatures of the rectal across the tail base (TB) and the abdominal region (ADT) were measured using an innovative infrared photodiode thermometer. The invasive rectal temperature (RT) was determined using a clinical thermometer, which is the gold standard for measuring cow temperature. The rectal temperature (RT) of n = 75 cows was strongly correlated with the temperature of tail base (TB) and closely correlated with the abdominal region (ADT) with r = 0.85, and r = 0.74 respectively. The emissivity (ε), measured by reflection, is 98.9 ± 1%. The emissivity on the cattle surface varied from 0.975 to 0.989. Our innovative infrared photo diode thermometers get rid of the problems that come with measuring temperature, such as invasive, less invasive, stressful methods, it could be used for long-term monitoring of core body temperature, which is shown to be safe as it provides better precision for inferring the core body temperature of cows. The remote server gets the cows' temperatures through Bluetooth and sends them to a central location so that the cows' health can be checked on all the time.