Whatever you chose, it can be difficult for EMS folks to enter a locked house when the resident is unable to open the door.
EMS had to break into the old neighbor lady's house this winter, and there is some procedure/permission process to follow for that which adds delay. There is supposed to be a hidden key or lockbox combination on record with Life Alert or whoever, but that is only as good as the person making sure the key or box is actually where it is supposed to be. In this case, the key was supposed to be under a planter. Trouble was, no one could see the planter in the hard frozen 4' of snow covering it.
It took 15-20 minutes for the EMS team to get in her house, plus she had two locked doors to get through; one into a mud porch, and a second door from there to the kitchen.