Ankle Monitors are devices used by the intelligence agencies to keep track of criminals or potentially dangerous individuals.
Tracking Turk Barrett
Released from his sentence on parole, Turk Barrett was equipped with the ankle monitor to keep track on him. However, Barrett managed to disable the device, so he was able to live his apartment and return to his criminal life. When Barrett and other civilians were kidnapped by the Hand, Karen Page suggested to activate the device again, so the New York City Police Department could find them, to which Barrett reluctantly agreed, after Tyler murdered Jerry.
Tracking Wilson Fisk
During his imprisonment at the Presidential Hotel, the FBI equipped Wilson Fisk with a monitor to make sure that he would not leave his suite. However, Fisk managed to manipulate several FBI agents, including Tammy Hattley, so they would remove the tracker which allowed Fisk to keep his plans in motion.
Due to the violation of the Sokovia Accords, several Avengers were arrested and imprisoned inside the Raft. Clint Barton and Scott Lang decided to cut a deal with a government so they could return to their families. The authorities equipped both of them with monitors and appointed the FBI to keep track of them.
Prior to end of his house arrest, Lang accidentally got his leg outside of the house perimeter, so the device informed the FBI about the escape attempt. Jimmy Woo and a group of agents arrived at the house to search the place, although Lang had no motives to escape. Later, Hope van Dyne took Lang away from his house and put a monitor on giant ant to trick the FBI that he was still at home.
Despite several attempts to catch Lang outside of the house, Woo found him inside with the monitor. As Lang's house arrest concluded, Woo ordered Burleigh to remove the monitor from Lang's ankle and release him.
In chronological order:
- Ant-Man and the Wasp
- Avengers: Endgame