Well gps tagging would help to locate a body wouldn't it so maybe one that could be turned on and off in emergencies.
Its only the same as giving birth to a child so it can provide genetic material to save an older sibling or the like.
If it was available, i would use it. My dogs are microchipped, if it meant i could find my child dead or alive i would use it.
It would help the police, search and rescue teams, find a child quickly if it went missing however so, no scrambling of police helicopters.
It was just an idea not so much a serious one and of course it would be open to abuse, what isn't. But if only the parent or guardian held the ability to switch it on?.... And it would be removed at a certain age.. the more i think about it the more i would be tempted to use it.
There's nothing worse i could think of than the loss of a child then the added inability to find their body so i could lay them to rest.