Those wary of package thieves can now add an extra measure of security to their home. Amazon is officially launching its Key in-garage delivery service, which it began testing in 37 US cities earlier this year. Now, Amazon's Key service, including Key for Garage, is available for Prime customers in 50 US cities . The service is intended for customers with a myQ smart garage door opener, which allows you to open and close your garage door with your smartphone. You can now give Amazon couriers access to your garage, which allows them to place your packages securely inside.