An automatic pet feeder is a great idea. Lots of diabetic cat owners use them. I've never tried it, but one that seems popular with the diabetes crowd is the
PetSafe 5 Meal Feeder. You could probably rig it up with an ice-pack underneath, but most users don't seem to find it necessary unless they're away for more than a day. Adding a couple tbsp of water helps, and another option is to freeze the canned food in an ice-cube tray so that it slowly thaws out while in the feeder.