How would a surgically implanted bomb be detonated... GSM or manual detonation?
Cell phone operation is prohibited in flight. Plot foiled.
Seriously; any trigger would have to involve some external actuation. If its a contact placed under the skin, the individual could actuate it themselves. I don't know how easy it would be for the cabin crew/passengers to immobilize someone to prevent such action. How would they know exactly where the trigger was placed? If its by GSM (or other short range radio), the trigger signal could be provided by an accomplice on the aircraft. Or perhaps on the ground. But the attenuation of a subcutaneous receiver could render that somewhat problematic.
Its probably on a level with an underpants bomb. Not well researched by the perpetrators, so its probability of success is about as high as lighting a sweaty pair of BVDs.