I still remember when I had to be hooked up to an infusion pump for many hours at a time. In theory this was all pretty simple - I had a port (a permanent link to my blood system), the machine was hooked to the port, the machine was configured to deliver x ml per hour. Easy, right? Well ... moving my arm had a non-zero chance to trigger the alarm (alarm means "the machine has a problem to deliver the configured amount", please do something), moving in the bed had a higher chance, walking over the hospital corridor I could almost guarantee that at some point in a single walk (i.e. one length of the corridor) it would freak out and again start the alarm. And that's for a far easier system in very easy conditions. An insulin pump has to change what it delivers all the time and it has to work always. Sport, work, driving, running, ...