There's an assumption here that if you're going to be using your Google Glasses to open a garage door, you'd presumably be wearing them while you're driving. I hope they finish driver-less cars first.
Other uses listed in the patent include: "For example, target device 14 could be a household appliance or device, such as a refrigerator, television, dishwasher, audio system, video system, alarm system, thermostat, garage door, etc. Alternatively, target device 14 could be an office appliance or device, such as a copy machine, fax machine, projection system, security system, etc. Other examples of target device 14 are also possible."