In Episode I: The Phantom Menace, young Anakin Skywalker and his mother explain how the Tatooine slave owners prevent the slaves from escaping:
SHMI: All slaves have a transmitter placed inside their bodies somewhere.
ANAKIN: I've been working on a scanner to try and locate mine. Any attempt to escape, and they blow you up!
Anakin is eventually freed by Qui-Gon - and Watto respects the terms of the bet because he's afraid of potential retribution from the Hutts if he didn't. But there's no scene that shows or explains what happens to Anakin's implant.
Does the adult Darth Vader still have an explosive implanted somewhere in his body?
If so, and the Rebellion happened to discover the exact frequency or signal needed to detonate the explosive, could they remotely assassinate Darth Vader?