Slap a tiny solar-powered GPS unit and transmitter on each block. ~$10 of electronics is marginal compared to the $2000 of concrete for each block. If any break

Slap a tiny solar-powered GPS unit and transmitter on each block. ~$10 of electronics is marginal compared to the $2000 of concrete for each block. If any break, you already have a crane that you can use to move the block out of the way for repair; just hand it over to an operator who can do the special-case operation by hand. If you get a beacon unit with a MTBF of 10 years and not awful clustering you might get one to five failing per stack per day, so you'd probably be able to handle a hundred stacks with a single operator dedicated to remote failure-handling.