If it is cheap enough, it could be used to easily bypass infrared motion sensors.
I see one way you might be able to work around this: if you made a suit out of this stuff, and were somehow able to rig it so that all of the heat is dumped inside the suit, then it would be "invisible" to IR sensors. However, it would get really uncomfortable inside that suit really fast.
Also, even if it somehow magically absorbed all of the IR without re-radiating, it would still be possible to build IR sensors that detect it: if it's perfectly black in IR, it will show up as a "shadow" against a warmer background. To be invisible to IR, you need a suit that matches its temperature to the surroundings.
But more importantly it absorbs infrared light, and converts it to heat. Heat and light are not the same thing! True, hot things emit light, but that doesn't make them the same thing.
Most practically you can cool the device once the energy is heat. Or just dilute it in a heatsink.
That gave me an idea... if it were possible to make a sphere that had this coating on the outside and dumped the heat to the inside, you'd have a great heat source for a Stirling engine. This could work exceptionally well in space if you can use the light-absorbing sphere oriented so that it shaded the cool side of your engine, thus maximizing the temperature difference.