The alarms on the mobile and such is a good idea to remind you take your insulin, but if you ever have those moments of doubt whether or not you've injected you can get insulin pens with a built in memory device, they tell you how long it been since you last injected and how many units you had taken at the time, one such pen is the NovoPen Echo used for Novorapid insulin. You can also buy devices that fit on the end of pens, one is called Timesulin.