>>511402715Your suggestion allows for many failure points, including latency/lag, last second hamming/signal loss.
If you're too do that, you no ight want to look into a pulldown resistor depending on how sensitive your detonator is. This will stop a floating voltage from being present.
An explosive like hmtd usually won't even need a detonator, it would probably explode mid flight just from vibrations. People often loose their hand or worse just trying to get the shit in a jar.
As for shrapnel, pennies are zink, which kinda sucks. If you're going all out, steel isn't that expensive but weighs more which could either be a good thing or a bad thing