Complex sentence: Their device is set to detonate within 24 hours if their demand is not met, and has anti-tampering devices that will set it off if any attempt is made to move or disarm it.
Split into simpler sentences: Their device is set to detonate within 24 hours if the demand is not met. It is also equipped with anti-tampering devices that will set it off if any attempt is made to move or disarm it.