Some bombs can be hooked to the beating of one's heart. The heart stops beating for ten seconds (or pick a time of your own choosing) and BOOM, the bomb detonates.

I recall air marshals from the late 1960s or early 1970s. A fellow stopped me as I was walking up the ramp to the plane. I put my hands up--he had no gun in his hand--and I slowly turned a 360 degree circle. I asked him why he was stopping me. He asked if I had any weapons. I said no. He never did frisk me (the idiot). He'd stopped me because I had long hair--that was back in the day when I HAD hair. Sometimes, the decisions people make can be downright stupid. If memory serves, I was leaving for Montreal from Newark Airport.