The d-Nav Insulin Guidance Device was tested by more than 150 patients with both type one and type two diabetes at the Ulster Hospital in Dundonald over the past 18 months.It is around the size of a mobile phone and allows users to easily regulate their own insulin, which doctors say is crucial in the battle to control an illness which presents a huge health problem in Northern Ireland, affecting some 80,000 people, and can lead to blindness or loss of limbs.Dr Roy Harper described the d-Nav as being like a "doctor in your pocket".He said: "It is really straight forward and simple and very clever in what it does. It is like having me with you all of the time because it looks for patterns in your blood sugars and then gives insulin."In our evaluation with the patients it worked very, very well for many patients. It is like having a doctor in your pocket, an expert in your pocket with you all of the time. Every time you check your blood sugars and every time you need to inject your insulin it gives you that guidance ongoing."Treating diabetes in Northern Ireland costs £400m per year and the number of patients is rising.It is hoped the new device, developed by an American company and costing around £90 a month, will reduce the number of times people with diabetes need to visit their doctor.Michael Anyadike-Danes, who took part in the trial, said: "When I took my reading just before lunch it told me that my sugar level was higher than it should have been - about 8.2 rather than 7 - then advised me that I needed to take a little bit more insulin than I otherwise would at lunch."A normal test would just tell me I was 8.2, then I would have a prescription which was given to me when I was last at the hospital, possibly six months ago, telling me to take the same amount of insulin each day."That is not then adjusted for my current condition, so this allows me to react."Although the d-Nav device may not be suitable for all patients, and it may take some time before it is more widely available, experts at the Ulster Hospital are convinced it represents a significant breakthrough in the fight to control diabetes both in NI and across the world.Discussions are now taking place to introduce it in more trust areas here.