I have the same requirement, freezer in garage 15m from bungalow, could do with a wireless warning device, I have the wireless alarm but need a way to trigger it when freezer warning light comes on, why don't they fit a small voltage free jack plug type socket that works through small relay connected to warning light, I am hunting a gaget to do the job. My new chest freezer is A+ class so can go without power for 46 hours and food should still be safe. So many little thermometer alarms out there but none for this task, come on inventors take on the task to adapt them. Will have to think about baby monitor idea.