A couple things - the insulin currently on the market works too slowly for a pump right now to fully close the loop – this functionality – notifying the pump of exercise and eating is part of the user control needed in a "hybrid closed loop" such as this. The user's insulin sensitivity given before, during or after exercise are very different than at other times. Different types of exercise affects body differently as well –HIIT for example raises blood glucose for a couple hours during and after – and then will significantly increase the sensitivity to insulin and many type 1's will drop rapidly. Aerobic activity will tend to drop blood glucose rapidly on it's own. Notifying the pump allows you to drop the levels given – something users do on their own now.
