"secret device" is correct and usable in written English.
You can use it when referring to any sort of device that is kept secret or hidden from the public. For example, "The government was accused of using a secret device to spy on its citizens."
It was used as a secret device for centuries before descending down to the everyday world and being renamed the slide projector.
It's not a secret device anymore, and there are people like me who would actually base their buying decision on the kind of plans that are being offered with it.
Each playback device comes with a binary tree of secret device and processing keys.
Then he shows her the secret device hidden underneath the lapel on his jacket.
Eventually, staff writer and co-executive producer George Meyer pitched the idea that the truckers would have "a secret device, that actually did all the driving for them," called the Navi-Tron Auto-Drive System.
He's a limo driver who borrows the fancy tuxedo that belongs to his mysterious boss (Jason Isaacs), only to find that it's actually a high-tech defense system, wired with a million secret devices.
These cognitive illusions are used together with optical illusions that exploit the properties of light; visual illusions that exploit how the brain interprets images; memory illusions that exploit the reconstructive nature of our recollections; special effects such as explosions; and various gimmicks, including secret devices and mechanical artifacts.
By bringing the design in-house, the team can develop a specific ARM variant tailored specifically for the iPhone; or some super-secret device we don't know about.
Prosecutors said they planned to place a secret recording device on Mr. Green to get a taped confession from Mr. Melvin.
No, it isn't a stubborn Y2K glitch, a secret listening device installed on New Year's Day, or a flu strain that only appears every thousand years.
He prayed five times a day at the Islamic Centre in Irvine, Orange County, wearing white robes with a camera hidden in one of its buttons, and carried a set of car keys that contained a secret listening device.
