Find My Mac is an app on Apple devices that reveal the location of a computer when it connects to the internet. The idea is that it can help you find the computer if someone steals it. Other platforms have similar software (a lot of Android users use Airdroid, for example). Basic options work ok, but just like with password management, this is a job best done by industry professionals who focus on one product.
Prey is free for one user for up to 3 devices, and after you install it, you get to pretty much forget about it. It provides two things: the software which you install on your devices, and a website where you can report devices as missing.
The software installed on your devices can surreptiously communicate with the outside world while it's connected to the internet, allowing your device to provide more information than other tools. For example, if your device is a laptop with a webcam, when enabled, their software is able to take a picture with the webcam at pretty much any time (of whomever it is has your laptop at that point) without any evidence of having done so – that includes suppressing any built-in lights that usually illuminate.