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