One issue he doesn't talk about is that the sender can never for sure know that the pager received the message.

At one point I was interested to know if there were versions of the paging technology (for some critical application?) that tried to solve this by issuing multiple redundant messages over some amount of time, and the pager ignoring the redundant ones after the 1st one had been received?

Also would be interesting to hear how the many companies "divided up" cities, etc. to create a network.

I remember there used to be some convoluted way of dialing into a pager service and keying the numbers/text that you wanted to be shown on the recipient's screen, but have long forgotten it.