My guess would be that Clark's implant is some form of kryptonite in a leaded glass ampule. The leaded glass protects him from the worst of the effects of the kryptonite, but probably allows some leakage which prevents Clark from being able to fully power up.
The ampule is probably equipted with some sort of radio receiver and tiny explosive. If Clark should cross over, or through one of those wires it would trigger a signal to the receiver which would then trigger the explosive which would break the glass ampule allowing the kryptonite into Clark's system.
Trask, being the thorough paranoid that he was, probably made sure that any break in the wiring would also trigger the signal which would set off the small explosive and doom Clark either way.
No way out.
Perhaps Menzies won't have to execute Clark. Clark might feel that the only way he can get Lois to accept that they could never have a life together is to commit a 'noble' suicide by trying to leave the cell himself sometime when she was gone.
Poor kids...their love is doomed.
Tank (who thinks that perhaps Moyne could come back, use the rods to incapacitate Clark and drag him out of the cell, thus triggering the failsafe device)
