Artemis- Button Camera

Later that evening young Artemis had popped a button camera intothe air-conditioning duct at the rear of the Bentley.

All the better to keep an eye on our guests.

The female was interesting. Fascinating, in fact. The darts would wear off soon, and it would be intriguing to watch her reaction, much more so than that of the hirsute teenager, even though his broad forehead suggested intelligence and his general features had a lot in common with the Fowl family’s own.
...

The button camera was broadcasting to his cell phone and ten-year-old Artemis checked the screen occasionally as Butler guided him through Rathdown Park toward the lemur’s cage.
...

The Fowl Manor intruders had escaped the Bentley trunk with the help of an accomplice. Another nonhuman.

I am entering a new world here. These creatures are potentially more lucrative than a lemur. Should I abandon this venture and concentrate on the nonhumans?

Artemis maximized the volume on his handset, but the tiny microphone attached to the button camera could only pick up snatches of the conversation.
...

A minute passed with only the small revolting dwarflike thing in the screen, perching its disproportionately large backside on the rim of the trunk; then the female appeared, only to promptly disappear, Rathdown Park’s famous pylons filling the screen where she had been.

Artemis tightened his grip on the phone.

Invisibility? The energy involved in creating a reflective field or needed to generate high-speed vibration must be incredible.

He quickly navigated the phone’s menu and activated the digital thermal imager, a decidedly nonstandard option, and was relieved to see the female creature’s form blossom on screen in warm tones.

-The Time Paradox, Chapter 7