Patients with hydrocephalus have an abnormal build-up of fluid around the brain and need a tube surgically implanted to drain that fluid. Patients and their caregivers live with the constant fear that the tube will block. Warning symptoms include irritability, headaches and vomiting. Unfortunately, there is no way of telling when fluid build-up is causing a rise in brain pressure and potentially impeding blood flow to the brain (life threatening) except for a brain scan in hospital and possibly hospitalisation. The investigators want to improve the lives of patients with hydrocephalus. They have developed a tool for parents and caregivers to monitor the pressure in the brain remotely via a sensor placed alongside the drainage tube. The device has been shown to be safe and to give reliable brain pressure readings using a large animal model (sheep). This study is a first-in-human safety study to show it is safe for patient use.