Pediatric neurodevelopmental disorders (NDDs) as defined by the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition, Text Revision : intellectual disabilities, communication disorders, attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), specific learning disorder, and motor disorders together with closely associated pediatric neurological conditions such as cerebral palsy (CP) and epilepsy, present with symptom fluctuations and variable performance, making longitudinal assessment challenging. Conventional clinical scales, questionnaires, and caregiver diaries are largely subjective and offer limited temporal coverage. This review examines wearable technologies applicable to these conditions, focusing on measurable digital biomarkers and real-world clinical application. A narrative review was performed. Wearable technologies were categorized into motion trackers (accelerometers/gyroscopes, inertial measurement units [IMUs]), physiological monitors (photoplethysmography-derived heart rate and heart rate variability, and electrodermal activity), wearable electroencephalography (EEG)/brain sensors, smart glasses/cameras, and textile-based wearables. IMU and accelerometer based systems achieved posture and gait classification accuracies of approximately 85%, distinguished children with ADHD from controls with 80-90% accuracy, and detected stereotyped behaviors in children with ASD with sensitivities exceeding 90%. Wearable EEG demonstrated high performance for ASD classification (accuracy, 96%; sensitivity, 100%) and for automated sleep staging in epilepsy(accuracy, 80.8-83.5%), and also enabled seizure-related signal monitoring through detection of ictal fast activity. For tonic-clonic seizures, wearable devices achieved sensitivities of 89-94%, whereas tonic-seizure detection performance remains limited. Smartwatch vibrotactile stimulation reduced stereotyped behaviors and improved task performance, and wrist-worn biosignals enabled prediction of aggressive behavior approximately three minutes before onset. Augmented reality based smart glasses supported social-communication coaching in children with ASD. In children with CP, smart-shoe systems classified daily activities with high accuracy and quantified gait asymmetry. Wearables enable objective and continuous assessment of symptoms and behaviors in children with NDDs and related pediatric neurological conditions across real-world environments and are expanding toward personalized intervention. Remaining challenges include integration into clinical workflows (electronic medical record [EMR] linkage, clinician-friendly data summarisation, and reimbursement pathways), ethical and privacy considerations, and standardisation of validation protocols.