HughPickens.com writes: More than one million Americans live with Type 1 diabetes, an autoimmune condition in which the pancreas stops producing insulin, a hormone needed to turn sugar into energy. Now Kate Linebaugh writes at the WSJ that Jason Calabrese, a software engineer, followed instructions that had been shared online to hack an old insulin pump so it could automatically dose the hormone in response to his son's blood-sugar levels. The Calabreses aren't alone. More than 50 people have soldered, tinkered and written software to make such devices for themselves or their children. Initially, Calabrese worried about the safety of the do-it-yourself project. He built it over two months, and spent weeks testing. At first, he only tried it out on his son on weekends and at night. Once it performed well enough, he said it felt irresponsible not to use it on his 9-year-old son. "Diabetes is dangerous anyway. Insulin is dangerous. I think what we are doing is actually improving that and lowering the risk," says Calabrese. The home-built project that the Calabreses followed is known as OpenAPS. The only restriction of the project is users have to put the system together on their own. As long as the people tinkering with their insulin pumps aren't selling or distributing them, the FDA doesn't have a legal means to stop it. The system involves an outdated insulin pump that communicates with a small radio stick connected to a continuous glucose monitor, a computer motherboard and a battery pack. It is an outgrowth of another open-source project where caregivers developed software to remotely monitor blood-sugar levels. The size of the homemade system varies, and the one that Calabrese carries has come down from the size of a small shoebox to that of a headphone case. He wears his insulin pump and glucose monitor on his belt. "It is clearly for people who have some expertise in computer programming," says Bruce Buckingham. "What it shows is that people are anxious to get something going."