They don't have to force you into silence, they can force you thru duress not to be silent. All that is needed is some sort of incentive or leverage. (Keep up the good work citizen or ...)

If the actual system is robust enough to be a "dead-man" switch then you have to plan for "false positives/negatives" and have more than one person involved in the process in case of emergencies. This increases your social attack surface. Two people might be trusted if one is dead and didn't leave any evidence behind.