The tiny Seek XR thermal camera mounts directly into the microUSB connector on Android devices running version 4.3.1 (Jelly Bean) or later or onto Apple devices with Lightning connectors running iOS 7+.
This is no high speed thermal optic, but for its price ($299), it delivers loads of functionality. The sensor is strong enough to detect a heat signature up to 2,000 feet away, and a focusing feature lets you manually adjust sharpness on objects as close as eight inches.
It's touted for outdoors uses, but one issue I noted — one I hope the company addresses — is that any protective case over my Samsung Galaxy phone, such as an OtterBox, must be removed from the phone in order to fully insert the camera into the microUSB port. My camera also consumed a noticeable amount of battery life.

Image from the SEEK Thermal XR.
Photo Credit: Courtesy
Still, this is one cool tool. I could, indeed, clearly discern heat-generating items and beings throughout the yard in the dark. The camera clearly revealed where my home was "leaking" heat, especially around windows and doors. Home inspection applications are numerous. The company also touts the camera's ability to assist in night boating and bloodtrailing when hunting, among other things.
The Seek XR has a proprietary 206x156 sensor that captures 32,000 pixels across its field of view. Temperature differences between the pixels are translated into images you can see with your eyes. To activate the unit, you download an app. The app takes thermal photos and videos. For more, see www.thermal.com.