It's possible to track a device using WiFi signal strength and/or trilateration.

Trilateration is technically different than triangulation.

 

Google "github wifi beacons" to see the most popular projects working with WiFi beacons.

 

WiFi and Bluetooth are two general ways to track a device - or at least determine if it's within range, turned on, and has WiFi/Bluetooth turned on.

 

For example, there's a well-known tool called WiFiPhisher to create a Rogue Access Point and set up a KARMA Attack.

Another interesting script on Github is called flood-kick-sniff which uses the "Known Beacons" attack to identify devices.